Functions in Python

Last Updated: 11-09-2018

A function is a set of statements that take inputs, do some specific computation and produces output. The idea is to put some commonly or repeatedly done task together and make a function, so that instead of writing the same code again and again for different inputs, we can call the function.
Python provides built-in functions like print(), etc. but we can also create your own functions. These functions are called user-defined functions.

# A simple Python function to check 
# whether x is even or odd 
def evenOdd( x ): 
if (x % 2 == 0): 
print "even"
else: 
print "odd"
 
# Driver code 
evenOdd(2) 
evenOdd(3) 

Output:

even
odd

Pass by Reference or pass by value?
One important thing to note is, in Python every variable name is a reference. When we pass a variable to a function, a new reference to the object is created. Parameter passing in Python is same as reference passing in Java.

# Here x is a new reference to same list lst 
def myFun(x): 
x[0] = 20
 
# Driver Code (Note that lst is modified 
# after function call. 
lst = [10, 11, 12, 13, 14, 15]  
myFun(lst); 
print(lst) 

Output:

[20, 11, 12, 13, 14, 15]