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FUNCTIONS IN PYTHON
By : Mrs Sangeeta M Chauhan , Gwalior
10/23/2019
© Sangeeta M Chauhan, Gwalior
By: Sangeeta M Chauhan

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FUNCTIONS IN PYTHON
Def
Function is a piece of code written to carry out a specified task.
You can Pass Data(input) known as parameter to a function
A Function may or may not return any value(Output)
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3. There are three types of functions in Python
Built-in functions The Python interpreter has a number of functions built into it that are always available. They are listed here in alphabetical order.
User-Defined Functions (UDFs): The Functions defined by User is known as User Defined Functions. These are defined with the keyword def
Anonymous functions, which are also called lambda functions because they are not declared with the standard def keyword
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Functions vs Methods :
A method refers to a function which is part of a class. You access it with an instance or object of the class.
A function doesn’t have this restriction: it just refers to a standalone function. This means that all methods are functions, but not all functions are methods.
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5. Structure of Python Function
def functionname ( parameters ):
"function_docstring“
function_body
return [expression]
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DOC STRING
Python Docstring is the documentation string which is string literal, and it occurs in the class, module, function or method definition, and it is written as a first statement. 
Docstrings are accessible from the doc attribute for any of the Python object and also with the built-in help() function can come in handy.
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7. After execution of the program/function
>>> Info.__doc__
'This Function is to display info about author.'
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8. Without execution of Program/function
>>> use_doc.Info.__doc__
'This Function is to display info about author.'
>>>
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9. Example of Function Definition
Example for Creating a Function without parameter
In Python a function is defined using the def keyword:
>>> def MyMsg1():    print("Learning to create function")
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10. Example of Function Definition
Example for Creating a Function with parameter
>>> def MyMsg2( name ):
"This prints a passed string into this function"
print (name ,” is learning to define Python Function”)
return
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11. Calling function MyMsg1 ()
To call a function, use the function name followed by parenthesis:
>>> MyMsg1()
Output :
>>> Learning to create function
Calling Function MyMsg2() twice with different parameter
>>> MyMsg2(‘Divyaditya’)
>>> MyMsg2(‘Manasvi’)
Output
Divyaditya is learning to define Python Function
Manasvi is learning to define Python Function
Parameters
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By: Sangeeta M Chauhan

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17. ?????Arguments Vs Parameters
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Function Arguments
1. Default 2. Positional 3. Keyword 4. Arbitrary(Variable no.)
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19. Variable no. of arguments
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20. Global and Local Variables in Python
a=50 # Global Variable def MyFunc(): b=100 # Local Variable print("Function Called :",a) print("Function Called :",b)
>>>MyFunc() # Function Call
Output
>>> Function Called 50
>>> Function Called 100
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21. Local and Global Variable……..
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The globals() method returns the dictionary of the current global symbol table. A symbol table is a data structure maintained by a compiler which contains all necessary information about the program
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MOST USEFUL BUILT-IN FUNCTIONS
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24. Syntax :Filter(function, sequence)
Returns an Object containing sequence of the items from the sequence for which function(item) is true
Syntax :Filter(function, sequence)
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By: Sangeeta M Chauhan

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Example
Computes primes up to 20
output
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26. Ex: map (factorial, list)
Calls function(item) for each of the sequence’s items
Syntax:
map(function, sequence)
Ex: map (factorial, list)
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27. Example of Map function
Computes the factorial of given values
output
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28. (Anonymous Functions)
Python lambda
(Anonymous Functions)
A lambda function is a small anonymous function.
A lambda function can take any number of arguments, but can only have one expression.
Syntax
lambda <arguments> : <expression>
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29. Example 1 of lambda function
output
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30. Example 2 : lambda Function
output
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31. Example 3: lambda Function
output
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32. Calling of functions with ternary operator.
OUTPUT
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33. # Function argument unpacking
output
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Output
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Thanks
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