A function is a block of organized, reusable code that is used to perform a single, related action. Functions help in organizing code. Functions provide better modularity for your application and a high degree of code reusing.

As you already know, Python gives you many built-in functions like print(), etc., but you can also create your own functions. These functions are called user-defined functions.

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Python provides some basic user defined functions that are built-in. Programmers can also build their own functions. There are many built in functions in Python and it is not possible to describe all over here. However, the following table explains some of the commonly used built in functions.

Function Description
abs(x) To get the absolute value of number x.
all(iterable) If all elements of the iterable are true, then this function will return a true
any(iterable) If any element of the iterable is true, then this function will return true
basestring() Used to check if an object is a string or a unicode
bin(x) Convert integer to a binary string
bool(x) Converts a value to boolean –and  returns true or false
bytearray(obj) If obj is callable it returns true else it returns false
chr(i) For I in the range of 0 to 255 it returns a string of one character whose ASCII code is the integer i

For objects x and y, the function returns negative integer if x

zero if x==0 and

positive integer is x>y

complex([real[, imag]]) Converts string or a number into a complex number.
delattr(object, name) This function helps in deleting an attribute of an object. The object should have a attribute with the name.
dict() Creates object of dictionary class
divmod(a,b) Where a and b are two non complex numbers, the function will return a pair of numbers that returns quotient and remainder.
file(name[, mode[, buffering]]) Constructor function for the file type
filter(func, iterable) Construct a list from those elements of iterable for which function returns true
Float([x]) Converts x to number of floating point. If x is a string object then it must contain a decimal or a floating point number
frozenset([iterable]) Returns frozenset object
getattr (object, name) Is same as object.name
hasattr (object, name) If name is one of the attributes of the object then it returns true or else false is returned
id(object) Returns identity of the object
int(n) Convert n to integer
len(s) Returns length of objects
long(n) Converts n to long
max(n) Return largest item of string, tuple or list
min(n) Return smallest item of string, tuple or list
pow(x,y) Result is x raised to the power of y
round(j,k) Floating point value of j is rounded to k digits

For defining your own functions, you will have to remember the following:

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1. A function is defined with the help of the keyword def

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2. The function name must end with parentheses ‘()’ followed by colon ‘:’ The syntax for defining a function is as follows:

def function_name(args):


Functions are completely independent of the main program. You may consider it as a mini independent program that may require some parameters for execution. The main program will only about the value returned by the function, and it is not concerned about what is actually done.

-Once a function has been designed it can be called from anywhere in the program




def whoAmI(str):
print ‘I am’,str
c =’Cat’

Output: I am Apple; I am 7; I am Cat

-Making a function return a value


def function_name():

code_to execute

return value


def whoAmI(str):
return str
c =’Cat’
print whoAmI(a)
print whoAmI(b)
print whoAmI(c)

output: I am Apple; I am ball; I am Cat


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