157 Python Functions

 7) Functions

1-Function is defined using the def keyword.

2-Arguments/parameters:

Arguments/parameters are specified in parenthesis after function name.

n number of arguments can be added.

3- function_docstring is optional.

4-return exists a fucntion

# Python fucntion syntax

def functionname( parameters ):

   "function_docstring"

   function_suite

   return [expression]

# simple python function

def hi():

    print ('hello')

hi() #to call function

Pass by reference vs value:

Parameters/arguments in Python are passed by reference. 

Means if you change what a parameter refers to within a function, change also reflects back in the calling function. 

# Pass by reference vs value

def paas_by_ref( mylist,mylist1 ):

   "This changes a passed list into this function"

   mylist.append([1,2,3]);

   mylist1.extend([1,2,3]);

   print ("Values inside function: ", mylist)

   print ("Values inside function mylist1: ", mylist1)

   return

# calling paas_by_ref function

mylist = [10,20,30];

mylist1 = [10,20,30];

paas_by_ref( mylist, mylist1  );

# paas_by_ref(  );

print ("Values outside function: ", mylist)

print ("Values outside function mylist1: ", mylist1)

Return statement:

def return_func( arg1, arg2 ):

   # Add both the parameters and return them."

   total = arg1 + arg2

   print ("Inside function : ", total)

   return total;

# # Now you can call sum function

return_func( 10, 20 );

Function Arguments:

You can call a function by using following types of arguments:

• Required arguments

• Keyword arguments

• Default arguments

• Variable-length arguments

# Required arguments

def args_func( str ):

   "This prints a passed string into this function"

   print (str)

   return;

# Now you can call printme function

args_func()  # pass args here otherwise gets error

# keyword arguments

def args_func (name1, name2):

   "This prints a passed info into this function"

   print ("Name1: ", name1)

   print ("NAme2: ", name2)

   return;

# Call  function

args_func (name1='a', name2="b")

# Default arguments

def keyword_args (name1, name2='b'):

   "This prints a passed info into this function"

   print ("Name1: ", name1)

   print ("NAme2: ", name2)

   return;

# Call  function

keyword_args (name1='a')

# Variable length arguments

def args_func (name1, *name2):

   "This prints a passed info into this function"

   print ("Name1: ", name1)

   print ("Name2: ", name2)

   return;

# Call  function

# for *name2, we can pass 0 or n args

args_func ('a')