Python Functions Tutorial | Working With Functions In Python | Python Training | Edureka

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Agenda
Python Functions

Agenda
Introduction 01
Why use Functions?
Getting Started 02
Concepts 03
Practical Approach 04
What are functions?
Looking at code to
understand theory
Types of functions

Why Use Functions
Python Functions

Why Use Functions?
Fahrenheit = (9/5)Celsius + 32
#collect input from user
celsius = float(input(“Enter Celsius value:
"))
#calculate value in Fahrenheit
Fahrenheit = (celsius*1.8) + 32
print(“Fahrenheit value is “,fahrenheit)
Logic to calculate Fahrenheit
Program to calculate Fahrenheit
You write a program in which Celsius must be converted to Fahrenheit multiple times
celsius = float(input(“Enter Celsius
value: "))
value: "))
value: "))
value: "))
value: "))
You wouldn’t want to repeat
those same lines of code every
time a value needed conversion
Reuse:

Why Use Functions?
Flip Channels
Adjust Volume
Functions are reusable tasks
DRY – Don’t Repeat Yourself
Functions reduce lines of code in your main program by letting you avail predefined
features multiple times without having to repeat its set of codes again.

What are Functions?
Python Functions

What Are Functions?
A function is a block of organized, reusable code that is used to perform some task.
• It is usually called by its name when its task needs execution.
• You can also pass values to it or have it return results to you.
‘def’ keyword before its name. And its name is to be followed by parentheses, before a colon(:).
def function_name():
“””This function does nothing.”””
pass
Functions are tasks that one wants to perform.
Def keyword:
Functions provide a way to break problems or processes down into smaller and independent blocks of code.

Docstring
>>> print(greet.__doc__)
This function greets to
the person passed into the
name parameter
Example
Remember this!
The first string after the function header is called the docstring and is short for documentation string.

Types of Functions
Python Functions

Functions
Functions
Built-in functions User defined functions

Built-in Functions in Python
Python Functions

abs() function
The abs() function returns the absolute value of the specified number.Definition
Syntax abs(n)
Example x = abs(3+5j)
C:UsersMy Name>python demo_abs_complex.py
5.830951894845301

all() function
The all() function returns True if all items in an iterable are true,
otherwise it returns False.Definition
Syntax all(iterable)
Example
mylist = [True, True, True]
x = all(mylist)
C:UsersMy Name>python demo_all.py
True
Same for lists, tuples
and dictionaries as well!

ascii() function
The ascii() function returns a readable version of any object (Strings,
Tuples, Lists, etc).Definition
Syntax ascii(object)
Example x = ascii("My name is
Ståle")
C:UsersMy Name>python demo_ascii.py
'My name is Ste5le'

bool() function
The bool() function returns the boolean value of a specified object.Definition
Syntax bool(object)
Example x = bool(1)
C:UsersMy Name>python demo_bool.py
True

enumerate() function
The enumerate() function takes a collection (e.g. a tuple) and returns it
as an enumerate object.Definition
Syntax enumerate(iterable, start)
Example x = ('apple', 'banana', 'cherry')
y = enumerate(x)
C:UsersMy Name>python demo_enumerate.py
[(0, 'apple'), (1, 'banana'), (2, 'cherry')]

format() function
The format() function formats a specified value into a specified format.Definition
Syntax format(value, format)
Example x = format(0.5, '%')
C:UsersMy Name>python demo_format.py
50.000000%

getattr() function
The getattr() function returns the value of the specified attribute from
the specified object.Definition
Syntax getattr(object, attribute, default)
Example
class Person:
name = "John"
age = 36
country = "Norway"
x = getattr(Person, 'age')
C:UsersMy Name>python demo_getattr.py
36

id() function
The id() function returns a unique id for the specified object.Definition
Syntax id(object)
Example
x = ('apple', 'banana', 'cherry')
y = id(x)
C:UsersMy Name>python demo_id.py
56450738

len() function
The len() function returns the number of items in an object.Definition
Syntax len(object)
Example
mylist = "Hello"
x = len(mylist)
C:UsersMy Name>python demo_len2.py
5

map() function
The map() function executes a specified function for each item in a
iterable. The item is sent to the function as a parameter.Definition
Syntax map(function, iterables)
Example
def myfunc(n):
return len(n)
x = map(myfunc, ('apple', 'banana’, 'cherry'))
C:UsersMy Name>python demo_map.py
<map object at 0x056D44F0>
['5', '6', '6']

min() function
The min() function returns the item with the lowest value, or the item
with the lowest value in an iterable.Definition
Syntax min(n1, n2, n3, ...)
Example x = min(5, 10)
C:UsersMy Name>python demo_min.py
5

pow() function
The pow() function returns the value of x to the power of y (x^y).Definition
Syntax pow(x, y, z)
Example x = pow(4, 3)
C:UsersMy Name>python demo_pow.py
64

print() function
The print() function prints the specified message to the screen, or other
standard output device.Definition
Syntax print(object(s), separator=separator, end=end, file=file, flush=flush)
Example print("Hello World")
C:UsersMy Name>python demo_print.py
Hello World

setattr() function
The setattr() function sets the value of the specified attribute of the
specified object.Definition
Syntax setattr(object, attribute, value)
Example
class Person:
name = "John"
age = 36
country = "Norway"
setattr(Person, 'age', 40)
C:UsersMy Name>python demo_setattr.py
40

sorted() function
The sorted() function returns a sorted list of the specified iterable
object.Definition
Syntax sorted(iterable, key=key, reverse=reverse)
Example
a = ("b", "g", "a", "d", "f", "c", "h", "e")
x = sorted(a)
print(x)
C:UsersMy Name>python demo_sorted.py
['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h']

type() function
The type() function returns the type of the specified objectDefinition
Syntax type(object, bases, dict)
Example
a = ('apple', 'banana', 'cherry')
b = "Hello World"
c = 33
x = type(a)
y = type(b)
z = type(c)
C:UsersMy Name>python demo_type.py
<class 'tuple'>
<class 'str'>
<class 'int'>

User Defined Functions in Python
Python Functions

User-Defined Functions In Python
Code first approach, let’s begin
def my_function():
print("Hello from a function")
Creating a function
def my_function():
print("Hello from a function")
my_function()
Calling a function

Parameters
Information passed to functions
def my_function(fname):
print(fname + " Refsnes")
my_function("Emil")
my_function("Tobias")
my_function("Linus")
Example
C:UsersMy Name>python demo_function_param.py
Emil Refsnes
Tobias Refsnes
Linus Refsnes

Parameters
Default parameter value
def my_function(country =
"Norway"):
print("I am from " + country)
my_function("Sweden")
my_function("India")
my_function()
my_function("Brazil")
Example
C:UsersMy Name>python
demo_function_param2.py
I am from Sweden
I am from India
I am from Norway
I am from Brazil

Parameters
Return values
def my_function(x):
return 5 * x
print(my_function(3))
Example
C:UsersMy Name>python
demo_function_return.py
15
25
45

Parameters
Recursion
def tri_recursion(k):
if(k>0):
result = k+tri_recursion(k-1)
print(result)
else:
result = 0
return result
print("nnRecursion Example Results")
tri_recursion(6)
Example
C:UsersMy Name>python demo_recursion.py
Recursion Example Results
1
3
6
10
15
21
Function

Python Lambda Function
Python Functions

Lambda Function
A lambda function is a small anonymous function. It can take any
number of arguments, but can only have one expression.
What is Lambda?
lambda arguments : expression
Syntax
x = lambda a : a + 10
print(x(5))
Example
C:UsersMy Name>python demo_lambda.py
15

Lambda Function
x = lambda a, b : a * b
print(x(5, 6))
A lambda function that multiplies argument a
with argument b and print the result: C:UsersMy Name>python demo_lambda2.py
30
x = lambda a, b, c : a + b + c
print(x(5, 6, 2))
A lambda function that sums argument a, b,
and c and print the result: C:UsersMy Name>python demo_lambda3.py
13

Why Use Lambda Function?
The power of lambda is better shown when you use them
as an anonymous function inside another function.
def myfunc(n):
return lambda a : a * n
mydoubler = myfunc(2)
print(mydoubler(11))
Use that function definition to make a
function that always doubles the number you
send in: C:UsersMy Name>python demo_lambda_double.py
22
def myfunc(n):

Why Use Lambda Function?
def myfunc(n):
mydoubler = myfunc(2)
mytripler = myfunc(3)
print(mydoubler(11))
print(mytripler(11))
Or, use the same function definition to make
a function that always triples the number you
send in: C:UsersMy Name>python demo_lambda_both.py
22
33

Conclusion
Python Functions

Conclusion
Python Functions, yay!

Python Functions Tutorial | Working With Functions In Python | Python Training | Edureka

Python Functions Tutorial | Working With Functions In Python | Python Training | Edureka

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