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Learn Python From Scratch - Functions & Strings

January 17, 2018 Unknown 1

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<span style="line-height: 107%;">Hi guys, hope you all are catching
along with previous Learn Python From Scratch tutorial, in this post you will
come across python functions and string operations. <span style="font-size: 12pt;"><o:p></o:p></span></span></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhe6uYknTgHztRs5a1cT7KWlcC9IRCyFijc3WX3rB5BEstamS2iIua_xMtQ7kCzoUGIgy0fcHif_OYpq6HOANJzDpZjBIb4miyqh7jV_rttHphAiPurNfqS5YPdebPf8SLNbOtLvDOPE0M/s1600/function1.PNG" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em; text-align: center;"><img border="0" data-original-height="324" data-original-width="754" height="136" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhe6uYknTgHztRs5a1cT7KWlcC9IRCyFijc3WX3rB5BEstamS2iIua_xMtQ7kCzoUGIgy0fcHif_OYpq6HOANJzDpZjBIb4miyqh7jV_rttHphAiPurNfqS5YPdebPf8SLNbOtLvDOPE0M/s320/function1.PNG" width="320" /></a><span style="line-height: 107%;"><b><span style="font-size: large;">Functions</span></b><span style="font-size: 12pt;"> </span>are a construct to structure
programs. They are known in most programming languages, sometimes also called <b>subroutines</b>
or <b>procedures</b>. Functions are reusable piece of code that can be invoked as many
times as required in the program and perform certain task.<o:p></o:p></span></div>
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<span style="line-height: 107%;">In Python a function is some reusable
code that takes arguments(s) as input, does some computation, and then returns
a result or results. We define a function using the def reserved word. We
call/invoke the function by using the function name, parentheses, and arguments
in an expression </span></div>
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<span style="line-height: 107%;"><span style="font-size: large;"><b>There are two kinds of functions in python.</b></span><o:p></o:p></span></div>
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<span style="line-height: 107%;">- 
Built-in functions that are provided as part of Python library -
print(), input(), type(), float(), int()<o:p></o:p></span></div>
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<span style="line-height: 107%;">- 
Functions that we define ourselves and then use<span style="font-size: 12pt;"><o:p></o:p></span></span></div>
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<span style="line-height: 107%;"><b><span style="font-size: large;">Building our own function:</span></b></span></div>
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<ul>
<li>We create a new
function using the def keyword followed by optional parameters in parentheses</li>
<li>We indent the body of
the function</li>
<li>This defines the
function but does not execute the body of the function</li>
</ul>
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<span style="line-height: 107%;"><b><span style="font-size: large;">Docstring:</span></b><span style="font-size: 12pt;"> </span>The first string after the
function header is called the docstring and is short for documentation string.
It is used to explain in brief, what a function does.<o:p></o:p></span></div>
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<span style="line-height: 107%;">Although optional, documentation is a
good programming practice. Unless you can remember what you had for dinner last
week, always document your code.<o:p></o:p></span></div>
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<span style="line-height: 107%;">In the above example, we have a
docstring immediately below the function header. We generally use triple quotes
so that docstring can extend up to multiple lines. This string is available to
us as __doc__ attribute of the function. For example:<o:p></o:p></span></div>
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<span style="line-height: 107%;">def greet(name):<o:p></o:p></span></div>
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<span style="line-height: 107%;">            """This
function greets to the person passed in as parameter"""<o:p></o:p></span></div>
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<span style="line-height: 107%;">            print("Hello,
" + name + ". Good morning!")<o:p></o:p></span></div>
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<span style="line-height: 107%;">Try running the following script with
the below addition: <o:p></o:p></span></div>
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print(greet.__doc__)</div>
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<span style="line-height: 107%;">You will get the output on your console as,</span></div>
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<span style="line-height: 107%;">>>> This function greets to
the person passed into the name parameter<o:p></o:p></span></div>
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<span style="line-height: 107%;">This is the end of the first topic of
discussion in this post which was functions. Now let’s see what does <b>"Strings"</b> in
python have to offer to a programmer.<span style="font-size: 12pt;"><o:p></o:p></span></span></div>
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<span style="line-height: 107%;"><span style="font-size: large;">A <b>String,</b></span></span></div>
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<ul>
<li>contiguous
series of characters delimited by single or double quotes<span style="font-size: 12pt;">. </span></li>
<li>A string literal is initialised with values in quotes. </li>
<li>Python
don’t have any separate data type for characters, so they are represented as a
single character string. </li>
<li>Strings in python are immutable, i.e. that once string
is created it can’t be modified.<span style="font-size: 12pt;"> </span></li>
<li>For strings, + operator
means “concatenate”. </li>
<li>When a string contains numbers, it is still a string but
they can be converted into numbers int().</li>
</ul>
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<span style="line-height: 107%;">We can get at any single character in
a string using an index specified in square brackets. The index value must be
an integer and starts at zero. If you try to attempt to access using index
beyond the length of the string python gives a traceback. The built-in function
to check the length of the string is len(). The string operations offered by
python are:<o:p></o:p></span></div>
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The method startswith() checks whether string starts with
str, optionally restricting the matching with the given indices start and end. </div>
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<span style="line-height: 107%;">It
has the following syntax:<o:p></o:p></span></div>
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<span style="line-height: 107%;"><b>str.startswith(str,
beg=0,end=len(string))</b>;<o:p></o:p></span></div>
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The replace() function is like a “search and replace”
operation in a word processor. It replaces all occurrences of the search string
with the replacement string. </div>
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<span style="line-height: 107%;">1. We use the <b>find()</b> function to search for a substring within
another string. </span></div>
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<span style="line-height: 107%;">2. <b>find()</b> finds the first occurrence of the substring. </span></div>
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<span style="line-height: 107%;">3. If the
substring is not found, <b>find()</b> returns -1.</span><o:p></o:p></div>
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 <span style="text-align: justify;">Slicing a string is a powerful tool in python strings wherein we can extract some part of a string. Slicing is performed using colon operator. We extend the square-bracket syntax a little, so that we can specify not only the starting position of the piece we want, but also where it ends. If we leave off the first number or the last number of the slice, it is assumed to be the beginning or end of the string respectively.</span><br />
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You can use ( > , <, <= , <= , == , !=  ) to compare two strings.<br />
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Python compares
string lexicographically i.e using ASCII value of the characters.<br />
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<span style="line-height: 107%;">1. Sometimes we want to take a string and remove whitespace at
the beginning and/or end.<o:p></o:p></span></div>
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<span style="line-height: 107%;">2. lstrip() and rstrip() remove whitespace at the left or right.<o:p></o:p></span></div>
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<span style="line-height: 107%;">3. strip() removes both beginning and ending whitespace.</span><o:p></o:p></div>
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<span style="line-height: 107%;"><span style="font-size: large;">Here are some of the most common
string methods,</span></span></div>
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<ol>
<li><b>s.lower(),
s.upper()</b> -- returns the lowercase or uppercase version of the string</li>
<li><b>s.strip() </b>--
returns a string with whitespace removed from the start and end</li>
<li><b>s.isalpha(), s.isdigit(), s.isspace().</b>..
-- tests if all the string chars are in the various character classes</li>
<li><b>s.startswith('other'),
s.endswith('other')</b> -- tests if the string starts or ends with the given other
string</li>
<li><b>s.find('other')</b>
-- searches for the given other string (not a regular expression) within s, and
returns the first index where it begins or -1 if not found</li>
<li><b>s.replace('old',
'new')</b> -- returns a string where all occurrences of 'old' have been replaced by
'new'</li>
<li><b>s.split('delimiter')</b>
-- returns a list of substrings separated by the given delimiter. The delimiter
is not a regular expression, it's just text. 'aaa,bbb,ccc'.split(',') ->
['aaa', 'bbb', 'ccc']. As a convenient special case s.split() (with no
arguments) splits on all whitespace chars.</li>
<li><b>s.join(list)</b> --
opposite of split(), joins the elements in the given list together using the
string as the delimiter. e.g. '---'.join(['aaa', 'bbb', 'ccc']) ->
aaa---bbb---ccc</li>
<li><b>s.replace(str1,
str2)</b> – this function is like search and replace operations where ot replaces
all occurences of the search string str1 by the replacement string str2.</li>
</ol>
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So here we are, at the end of the
post, lets summarize the topics we have seen today. Functions: What are they? Why are they used? How can we define a function? Strings: What are they? How are they used and various methods that provide some meaningful operations perform-able to these string. This concludes the
post, stay tuned for the next post on the topic of file operations, until then
guys enjoy your time browsing through other posts in the blog!! Please leave your questions in the comments section if any. </div>
</div>

Tutorials Learn Python From Scratch - Functions & Strings

Python – Functions and strings Hi guys, hope you all are catching along with previous Learn Python From Scratch tutorial, in this post you will come across python functions and string operations. Functions are a construct to structure programs. The…

Learn Python from Scratch - Conditional Execution

January 13, 2018 Unknown 2

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Ola pythonista's, so this is a follow
up of the previous post which was on the introduction of python. Here, I’m
going to talk about Conditional execution and iterations in python. Hope you
would find it interesting to browse.<o:p></o:p></div>
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<br /></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhZDJ7-NJ0dvU0AVIzJX5BjE-sgsf6Q-3niLMUntG7VofImNgX1Mq2AeL3sKjy6nTvxFcHpk9nYZc1o1PCThvvnlvO95xIYJ0gTeIjh7HD-8qzWq_SHpn-n6cSo82K1aUSDUP7JxVbZjew/s1600/if.PNG" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em; text-align: center;"><img border="0" data-original-height="417" data-original-width="782" height="170" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhZDJ7-NJ0dvU0AVIzJX5BjE-sgsf6Q-3niLMUntG7VofImNgX1Mq2AeL3sKjy6nTvxFcHpk9nYZc1o1PCThvvnlvO95xIYJ0gTeIjh7HD-8qzWq_SHpn-n6cSo82K1aUSDUP7JxVbZjew/s320/if.PNG" width="320" /></a>There are many conditional constructs
in python, and the first one we are going to see is the unidirectional
branching statement, the prodigal construct: “if”.<o:p></o:p></div>
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An if statement precedes with a
condition that is checked and is recouped to a boolean expression and if it’s
results to true then a set of statement are executed otherwise they’re skipped
and the instructions after the construct body is executed. <o:p></o:p></div>
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Boolean expressions in python use
the following relational operators:</div>
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<o:p></o:p></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi8iW1etxVQ-lztvQqCdFQ-BIPt8SDPZx55lF3gA4X_Uj_xyNP9IDOd1t9Qc9SpD5KBqQU_Ww14jmmNG4B4LlewO-iAthRDLZQvsNG_UxNofHUioMjWInQQU33xC3cUIGVmg0mUAtKckLw/s1600/relational_operators.PNG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="291" data-original-width="403" height="231" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi8iW1etxVQ-lztvQqCdFQ-BIPt8SDPZx55lF3gA4X_Uj_xyNP9IDOd1t9Qc9SpD5KBqQU_Ww14jmmNG4B4LlewO-iAthRDLZQvsNG_UxNofHUioMjWInQQU33xC3cUIGVmg0mUAtKckLw/s320/relational_operators.PNG" width="320" /></a></div>
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Indentation is an important
prospect of python programming language as the language doesn’t use the usual
flower braces to represent a construct body as in other high-level languages as
C++ or Java and hence an increase indent after conditional or looping statement
indicate the body of the construct and the indent is maintained to indicate the
scope of the block. To get back to level of the conditional or iteration
statement we reduce the indent to indicate the end of the block. <o:p></o:p></div>
<div>
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEikDEbuohK3Gy7m8Gbp3OgKYgHBQkhqpEp5FvVyKTCJF29WhXOEe5jEOVnjkRqA7kTQ2WwT_uk7IkljCiOku-1PsZ9WI_rWgD6RJtwptinWEGVDewyGyQ9IS_Omx35sa6nCpGCpNZaWVCA/s1600/meme1.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="525" data-original-width="790" height="212" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEikDEbuohK3Gy7m8Gbp3OgKYgHBQkhqpEp5FvVyKTCJF29WhXOEe5jEOVnjkRqA7kTQ2WwT_uk7IkljCiOku-1PsZ9WI_rWgD6RJtwptinWEGVDewyGyQ9IS_Omx35sa6nCpGCpNZaWVCA/s320/meme1.jpg" width="320" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiztEKIq6SlVkam175_uK2DEioTShQLJVSJv6eirf7RyOhpSHh_OGKBrdpn3cSYum5vr_FxEqYlLpnshYQZPFQMjimlSfs2JbrCn3iqW5CSekpGXsxtcFQPYood4030-7uBFIjGz_HwYc0/s1600/meme3.png" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em; text-align: center;"><img border="0" data-original-height="692" data-original-width="720" height="307" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiztEKIq6SlVkam175_uK2DEioTShQLJVSJv6eirf7RyOhpSHh_OGKBrdpn3cSYum5vr_FxEqYlLpnshYQZPFQMjimlSfs2JbrCn3iqW5CSekpGXsxtcFQPYood4030-7uBFIjGz_HwYc0/s320/meme3.png" width="320" /></a>Two-way decisions are possible in
python by using if-else construct wherein if the condition evaluates to true a
set of statement are executed otherwise the body in the else construct is
executed and finally executed the rest of the instructions after the
conditional construct. Below is a snippet that depict two-way decision.<o:p></o:p></div>
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//flowchart and snippet <o:p></o:p></div>
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Mutli-branching decision is
possible by using an if-elif-else construct, where in if the condition
evaluates to true executes a set of statements and skips execution of the rest
of the conditional construct otherwise evaluate the next condition that
precedes the elif statement and if that evaluates the condition to true then a
set of instructions are executed otherwise executes the statements in the else
body.</div>
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<o:p></o:p></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg15GBGtX75y8RVry1QvcuBuGiqer1vl7QnBUKoCLTAeeQ4qsb1zHAX2e8CkTQYq5GSvc-HBqeMUAmwqj4Ja_bNw4109B_4cxso_9IA74QKvfTT7jCA9nnBnNdhbucNp03vejcpp9Me3JQ/s1600/multiway.PNG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="382" data-original-width="696" height="218" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg15GBGtX75y8RVry1QvcuBuGiqer1vl7QnBUKoCLTAeeQ4qsb1zHAX2e8CkTQYq5GSvc-HBqeMUAmwqj4Ja_bNw4109B_4cxso_9IA74QKvfTT7jCA9nnBnNdhbucNp03vejcpp9Me3JQ/s400/multiway.PNG" width="400" /></a></div>
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This is the end of conditional
construct in python and before we can get to python iterations let’s discuss
about how to handle dangerous sections of code that raises an error that can be
maskable i.e. for which we can write a piece of code that acts when a set of
statements causes a traceback and tries to solve or bring the program out of
the troubleshoot problem else the program can terminate if not handled. This is
possible in python by use of the try/except structure. You surround a dangerous
section of code with try and except. If the code in the try works - the except
is skipped. If the code in the try fails - it jumps to the except section.<o:p></o:p></div>
<div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjbuc3wIMWqz_lj6qqM8asp2UwVIgvbd_r08WiBy5-J0rMHYpJVAWRjnL5REPBi1VwEiP1Y9QWCHoWm-lQNCjMYlS_-PsICu1ptp9ONat-4LCsCDY-kbSjYTb1QI7WzLdl9DBGloSDXDlI/s1600/try_except.PNG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="427" data-original-width="767" height="222" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjbuc3wIMWqz_lj6qqM8asp2UwVIgvbd_r08WiBy5-J0rMHYpJVAWRjnL5REPBi1VwEiP1Y9QWCHoWm-lQNCjMYlS_-PsICu1ptp9ONat-4LCsCDY-kbSjYTb1QI7WzLdl9DBGloSDXDlI/s400/try_except.PNG" width="400" /></a></div>
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Now let’s understand python iterations
which is last topic of this post. What are iterations?? <span style="background: white; color: #222222;">They’re repetition of a set of statements. They can
be categorized into two kinds – definite and indefinite.<o:p></o:p></span></div>
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<span style="background: white; color: #222222;"><br /></span></div>
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<span style="background: white; color: #222222;">While
loops are called “indefinite loops” because they keep going until a logical
condition becomes false. Sometimes it is a little harder to be sure if a loop
of such a kind will terminate or not. A while loop is written in a following
manner, its identified by the reserved word while and follows with a condition
that evaluates to a Boolean value and only if it’s true that the control flow
enter the loop body and hence the while loop is also called entry controlled
loop.<o:p></o:p></span></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhSRaX44XGkYi5yfyqPZW6ExiWEJOpkFMBJqA0TVyv6wbF10r7Yy1EyAuLiEyGc8z4H_LuENmAHGAceZzJarehZ7_5OdFmGq_PJ5pJyZHpusS6bDEV5Wgw79MUJ4_597PhkvQ8PpAIwCy4/s1600/while.PNG" imageanchor="1" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" data-original-height="404" data-original-width="798" height="202" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhSRaX44XGkYi5yfyqPZW6ExiWEJOpkFMBJqA0TVyv6wbF10r7Yy1EyAuLiEyGc8z4H_LuENmAHGAceZzJarehZ7_5OdFmGq_PJ5pJyZHpusS6bDEV5Wgw79MUJ4_597PhkvQ8PpAIwCy4/s400/while.PNG" width="400" /></a></div>
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<span style="background: white; color: #222222;"><br /></span></div>
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<span style="background: white; color: #222222;">For
loops are called “definite loops” because they execute the loop body for exact
number of times. We can write a loop to run the loop once for each of the items
in a set using the Python for construct. </span><span style="background-color: white; color: #222222;">Definite loops (for loops) have
explicit iteration variables that change each time through a loop.</span><span style="background-color: white; color: #222222;">  </span><span style="background-color: white; color: #222222;">These iteration variables move through the
sequence or set. The iteration variable “iterates” through the sequence
(ordered set). The block (body) of code is executed once for each value in the
sequence. The iteration variable moves through all of the values in the
sequence.</span></div>
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<span style="background: white; color: #222222;">The
“is” and “is not” operators in python that are used in logical expression. The
“is” operator implies is the same as but have more weight than the logical
operator “==”. The “is not” operator logically is opposite of the “is”
operator.<o:p></o:p></span></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEioTjgMDrCPiS4TbedK-HsoPKoXuhV6hjpvD6_EoRRls_EIgjqK0q96HIh2lztXMI7ld7IqNVg4-K0FFrIlWUcUxtj1CbZVlKC4xMs3xYDtH-pYdWULtjpp4nFC3uaXTCQsgdjF-n8YcWw/s1600/is.PNG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="247" data-original-width="420" height="188" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEioTjgMDrCPiS4TbedK-HsoPKoXuhV6hjpvD6_EoRRls_EIgjqK0q96HIh2lztXMI7ld7IqNVg4-K0FFrIlWUcUxtj1CbZVlKC4xMs3xYDtH-pYdWULtjpp4nFC3uaXTCQsgdjF-n8YcWw/s320/is.PNG" width="320" /></a></div>
<o:p></o:p><br />
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<span style="background: white; color: #222222;">So here
we are, at the end of the post, let’s summarise the topics we have seen today.
(……..) This concludes the post, stay tuned for the next post on the topic of functions
and string operations, until then guys enjoy your time browsing through other
posts in the blog!!</span><span style="text-align: left;"> </span></div>
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Tutorials Learn Python from Scratch - Conditional Execution

Ola pythonista's, so this is a follow up of the previous post which was on the introduction of python. Here, I’m going to talk about Conditional execution and iterations in python. Hope you would find it interesting to browse. There are many conditi…

Learn Python from Scratch - Introduction

January 12, 2018 Unknown 0

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<span lang="EN-US">Python is
the language of the Python Interpreter and those who can converse with it. An
individual who can speak Python is known as a Pythonista. It is a very uncommon
skill, and nearly all known <b>Pythonistas </b>use software initially developed by
Guido van Rossum.</span><o:p></o:p><br />
<span lang="EN-US"><br /></span></div>
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When we are at the python interpreter, it displays chevron
prompt (>>>) on the terminal, where it is asking you <b>“What’s next??”.</b></div>
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<o:p></o:p></div>
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<b><br /></b>
<b><br /></b>
<b><br /></b>
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<b><br /></b></div>
<div style="text-align: left;">
<b>How do we speak the language of python??</b><o:p></o:p></div>
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This must be the question on most of your minds when trying
to learn the language initially. Just like the English Language, we will first
start of by learning words, sentences and then paragraphs in python.<o:p></o:p></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjbqrH36G51V1wdlubB4rLMVK-UOwb5Sm-97rXkeIeAWItPY1bdil_g1BWIulw4GvsiIReEBxGpFZFPVQuRaPBvYjDs-sGPYJcTsxY4tdaGiFlfIyy4xmk5nSEb7jopDjv-cmEn6ZBe1FE/s1600/reserved-words.jpg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em; text-align: center;"><img border="0" data-original-height="197" data-original-width="481" height="162" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjbqrH36G51V1wdlubB4rLMVK-UOwb5Sm-97rXkeIeAWItPY1bdil_g1BWIulw4GvsiIReEBxGpFZFPVQuRaPBvYjDs-sGPYJcTsxY4tdaGiFlfIyy4xmk5nSEb7jopDjv-cmEn6ZBe1FE/s400/reserved-words.jpg" width="400" /></a><b>Reserved Words:</b> They’re words that are predefined in the
python library and have some meaning. These words cannot be used as variables
or as a matter of fact to do anything that these words don’t offer. Some of
these reserved words that we would come across are stated in the figure alongside.<o:p></o:p><br />
<br /></div>
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Constants and variables are other literals that are
supported by python. “<b>Constants</b>”, as the word suggests <span lang="EN-US">they’re fixed values such as numbers, letters,
and strings, where their value does not change</span> throughout the scope of
the program. <span lang="EN-US">A <b>variable </b>is a
named place in the memory where a programmer can store data and later retrieve
the data using the variable “name”</span>.<o:p></o:p></div>
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Since we programmers are given a choice in how we choose our
variable names, there is a bit of “best practice”, we name variables to help us
remember what we intend to store in them (“mnemonic” = “memory aid”). This can
confuse beginning students because well-named variables often “sound” so good
that they must be keywords. There are rules that have to be followed while
naming a variable so as to reduce ambiguity for the interpreter, and they’re:</div>
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</div>
<ol style="text-align: left;">
<li> <span style="text-indent: -18pt;">Must start with a letter or underscore _</span></li>
<li>Must consist of letters, numbers, and underscores</li>
<li>Case Sensitive</li>
<li>Cannot be Reserved Word.</li>
</ol>
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<o:p></o:p></div>
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Next comes sentences, or here we are specifically talking
about how do we code instruction in python. For simpler understanding let’s
start off with arithmetic expressions.<o:p></o:p></div>
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                Assignment
Statement: x=2<o:p></o:p></div>
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                Arithmetic
assignment: x=x+2<o:p></o:p></div>
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                Output
Statement: print(x)<o:p></o:p></div>
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So, what all did we come across in the previous three
instructions, operators, constants, variables and function.<o:p></o:p></div>
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<br /></div>
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Numeric Expressions that are used in python are mentioned
below, //pic of operator operation table <o:p></o:p></div>
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<br /></div>
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When we have so many operators for numeric expressions to
perform simple calculation, there must be a way python must know which of them
to do first, so to address this situation we will have to learn about the
concept of operator precedence, i.e. which operator takes precedence over the
others.<o:p></o:p></div>
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<span lang="EN-US"><br /></span></div>
<div class="MsoNormal">
<span lang="EN-US">Highest
precedence rule to lowest precedence rule:<o:p></o:p></span></div>
<div class="MsoListParagraphCxSpFirst" style="text-align: left; text-indent: -18pt;">
</div>
<ol style="text-align: left;">
<li>Parentheses are always respected</li>
<li>Exponentiation (raise to a power)</li>
<li>Multiplication, Division, and Remainder</li>
<li>Addition and Subtraction</li>
<li>Left to right</li>
</ol>
<o:p></o:p><br />
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Note: Remember in python3 when you perform integer division
it produces a floating-point result.</div>
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<o:p></o:p></div>
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<br /></div>
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Now lastly let’s see how to write paragraphs, Interactive
python is good for experimenting programs of 3 to 4 lines, but most programs
are much longer than that, so we type our python scripts in a file using an
editor and then we tell python to run those commands that we have coded in the
file. As a convention we add .py extension for python files. <o:p></o:p></div>
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<br /></div>
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<b>Sequential flow of execution</b> is followed by python
interpreter unless it comes across some branching, looping or conditional
statement. This means to say that when a program is running, that the flow of
execution occurs from one step to the next. As programmers we set paths for the
program to follow.<o:p></o:p></div>
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<br /></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiF_ENyI8hwXYX60oqY_aeYcBvrND5VJXOJn4sHv9ElnSCWwdLq0hoxqbZnUlh0ih6edFrKVxY7O_Dl03ulZeg7p8fk6NsXmkh2Uzhu5XN_gRIF_8WAQTpjtIRIwL2ZXQECxx9pDcbIZQ4/s1600/type.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em; text-align: center;"><img border="0" data-original-height="320" data-original-width="400" height="256" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiF_ENyI8hwXYX60oqY_aeYcBvrND5VJXOJn4sHv9ElnSCWwdLq0hoxqbZnUlh0ih6edFrKVxY7O_Dl03ulZeg7p8fk6NsXmkh2Uzhu5XN_gRIF_8WAQTpjtIRIwL2ZXQECxx9pDcbIZQ4/s320/type.jpg" width="320" /></a>In python the variables are not declared by the programmer
and the python interpreter resolves this during the interpretation time of the
program and hence the language is dynamic. Python knows what type everything
is, but some operators are prohibited as in you cannot add a numeric 1 to a
string. We can ask python what type some named space is by using the built-in
function, type().<o:p></o:p></div>
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</div>
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<br /></div>
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There are certain scenario when the programmer would
explicitly like to typecast a named space and to do so there are some built-in
functions available to us, such as:<o:p></o:p></div>
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<br /></div>
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<div style="text-align: right;">
</div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhXhSs8QKi33-XLraXLvR6I1gN6NN3mby9zFdWIarL44AdPL0A_nDKssFdkz-6OZPcHNjeKOg5yk8mgGUrl4gopGUMaE9iIHHOssP_hw2Ub72EeP37aGEzBVd6eZU7peGZu8gbwibZW7P0/s1600/typecasting.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" data-original-height="261" data-original-width="596" height="175" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhXhSs8QKi33-XLraXLvR6I1gN6NN3mby9zFdWIarL44AdPL0A_nDKssFdkz-6OZPcHNjeKOg5yk8mgGUrl4gopGUMaE9iIHHOssP_hw2Ub72EeP37aGEzBVd6eZU7peGZu8gbwibZW7P0/s400/typecasting.jpg" width="400" /></a></div>
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgkQnxEAjoK1MwBJAmFdCYunpmQwec5PSHobjUE4Qzf0HiQspOyta_FCEM9i8tLlwXK_NLIMtBEEYFLCDWGSVmzUinEVlNyPLz351m1dFs51ityVefMf1djL6D-L2o3wpncpzfrjZMj26E/s1600/input.jpg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em; text-align: center;"><img border="0" data-original-height="104" data-original-width="380" height="87" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgkQnxEAjoK1MwBJAmFdCYunpmQwec5PSHobjUE4Qzf0HiQspOyta_FCEM9i8tLlwXK_NLIMtBEEYFLCDWGSVmzUinEVlNyPLz351m1dFs51ityVefMf1djL6D-L2o3wpncpzfrjZMj26E/s320/input.jpg" width="320" /></a>For python script to be interactive it must take input from
the user and it does that by invoking a function, input() which takes a string
argument and returns a string object containing the value entered by the user.
The same operation is done by function raw_input() in python2.<o:p></o:p></div>
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<br /></div>
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Let’s say we want to read a number from the user then we
must convert the string object to integer or float using the typecasting
function which we have seen earlier.<o:p></o:p></div>
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<br /></div>
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<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmcPeQNxXihiQYDvcWURGCi__YRwEidGC5b6u0YWDJoiOM5FbtBwADuUx7Gas3lVcxU3SepJ85VrNXhlvz-hAe7elQIyikwJz9w2QgmuAj7JUmn1fcV9pJ1OBurHFDus6_Ks_JfrLWkoI/s1600/input_convert.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="250" data-original-width="314" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmcPeQNxXihiQYDvcWURGCi__YRwEidGC5b6u0YWDJoiOM5FbtBwADuUx7Gas3lVcxU3SepJ85VrNXhlvz-hAe7elQIyikwJz9w2QgmuAj7JUmn1fcV9pJ1OBurHFDus6_Ks_JfrLWkoI/s1600/input_convert.jpg" /></a></div>
<br /></div>
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<b>Comments </b>in python are prefixed by the ‘#’ symbol, when the
interpreter comes across a line prefixed with ‘#’ then it doesn’t execute it or
ignores it as comment. As a beginner in programming you might think why do we
need to write comments in a program, the reasons are,<o:p></o:p></div>
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<span lang="EN-US"> -  Describe
what is going to happen in a sequence of code</span><o:p></o:p></div>
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<span lang="EN-US"> - 
Document who wrote the code or other ancillary information</span><o:p></o:p></div>
<div class="MsoNormal">
<span lang="EN-US"> -  Turn
off a line of code - perhaps temporarily</span><o:p></o:p></div>
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<br /></div>
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So now we have come to the end of introduction in python,
and at this checkpoint we have pictured the edges of a big canvas about python
and we will focus on the details of this canvas in the next post. Stay tuned
for the next post on the topic of conditional statements and iterations, until
then guys enjoy your time browsing through other posts in the blog!!<br />
<br />
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<o:p></o:p></div>
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Python is the language of the Python Interpreter and those who can converse with it. An individual who can speak Python is known as a Pythonista. It is a very uncommon skill, and nearly all known Pythonistas use software initially developed by Guido…

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