Python Collections-Lists in Python

  • The Python tutorials are written as Jupyter notebooks and run directly in Google Colab—a hosted notebook environment that requires no setup. Click the Run in Google Colab button.


  • Colab link - Open colab


  • Python Functions - A function is a block of code which only runs when it is called.**


  • **You can pass data, known as parameters, into a function(Function_Name(Parameters)).**


  • **A function can return a value if specified.**


  • Answers to the exercises are given at the end of the notebook


  • **Creating a Function:** In Python a function is defined using the def keyword. 


    •  
def my_function():
  print("Hello from a function")

  • **Parameters:** Information can be passed to functions as parameter.


  • Parameters are specified after the function name, inside the parentheses. You can add as many parameters as you want, just separate them with a comma.


  • The following example has a function with one parameter (fname). When the function is called, we pass along a first name, which is used inside the function to print the full name. 


    •  
def my_function(fname):
  print(fname + " Refsnes")

my_function("Emil")
my_function("Tobias")
my_function("Linus")

  • **NOTE:** If we call the function without parameter, it uses the default value. 


    •  

def my_function(country = "Norway"):
  print("I am from " + country)

my_function("Sweden")
my_function("India")
my_function()
my_function("Brazil")

  • **Return Statement** When the function results in some value and that value has to be stored in a variable or needs to be sent back or returned for further operation to the main algorithm, return statement is used. 


    •  
def times(x,y):
    z = x*y
    return z

  • The above defined times( ) function accepts two arguements and return the variable z which contains the result of the product of the two arguements 


    •  
c = times(4,5)
print c


20

  • The z value is stored in variable c and can be used for further operations.


  • Instead of declaring another variable the entire statement itself can be used in the return statement as shown. 


    •  
def times(x,y):
   return x*y       # This multiplies the two input arguments and returns it.


c = times(4,5)
print c


20

  • Since the times( ) is now defined, we can document it as shown above. This document is returned whenever times( ) function is called under help( ) function.


  • **Implicit arguments** When an argument of a function is common in majority of the cases or it is "implicit" this concept is used. 


    •  
def implicitadd(x,y=3):
    return x+y

  • **implicitadd( )** is a function accepts two arguments but most of the times the first argument needs to be added just by 3.


  • Hence the second argument is assigned the value 3. Here the second argument is implicit. 


    •  
implicitadd(4)       # if the second argument is not defined when calling the implicitadd( ) function then it considered as 3.

  • But if the second argument is specified then this value overrides the implicit value assigned to the argument 


    •  
implicitadd(4,4)     # if the second argument is specified then this value overrides the implicit value assigned to the argument

  • ## ** Arbitrary arguments** If the number of arguments that is to be accepted by a function is not known then a asterisk symbol is used before the argument. 


    •  
def add_n(*args):
    res = 0
    reslist = []
    for i in args:
        reslist.append(i)
    print reslist
    return sum(reslist)

  • The above function accepts any number of arguments, defines a list and appends all the arguments into that list and return the sum of all the arguments.

  • add_n(1,2,3,4,5)