** Python Certification Training: https://www.edureka.co/python **
This Edureka PPT on Python Functions tutorial covers all the important aspects of functions in Python right from the introduction to what functions are, all the way till checking out the major functions and using the code-first approach to understand them better.
Agenda
Why use Functions?
What are the Functions?
Types of Python Functions
Built-in Functions in Python
User-defined Functions in Python
Python Lambda Function
Conclusion
Python Tutorial Playlist: https://goo.gl/WsBpKe
Blog Series: http://bit.ly/2sqmP4s
Follow us to never miss an update in the future.
Instagram: https://www.instagram.com/edureka_learning/
Facebook: https://www.facebook.com/edurekaIN/
Twitter: https://twitter.com/edurekain
LinkedIn: https://www.linkedin.com/company/edureka
3. Python Certification Training https://www.edureka.co/python
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
5. Python Certification Training https://www.edureka.co/python
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
#collect input from user
celsius = float(input(“Enter Celsius
value: "))
#calculate value in Fahrenheit
Fahrenheit = (celsius*1.8) + 32
print(“Fahrenheit value is “,fahrenheit)
#collect input from user
celsius = float(input(“Enter Celsius
value: "))
#calculate value in Fahrenheit
Fahrenheit = (celsius*1.8) + 32
print(“Fahrenheit value is “,fahrenheit)
#collect input from user
celsius = float(input(“Enter Celsius
value: "))
#calculate value in Fahrenheit
Fahrenheit = (celsius*1.8) + 32
print(“Fahrenheit value is “,fahrenheit)
#collect input from user
celsius = float(input(“Enter Celsius
value: "))
#calculate value in Fahrenheit
Fahrenheit = (celsius*1.8) + 32
print(“Fahrenheit value is “,fahrenheit)
#collect input from user
celsius = float(input(“Enter Celsius
value: "))
#calculate value in Fahrenheit
Fahrenheit = (celsius*1.8) + 32
print(“Fahrenheit value is “,fahrenheit)
You wouldn’t want to repeat
those same lines of code every
time a value needed conversion
Reuse:
6. Python Certification Training https://www.edureka.co/python
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.
8. Python Certification Training https://www.edureka.co/python
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.
9. Python Certification Training https://www.edureka.co/python
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.
13. Python Certification Training https://www.edureka.co/python
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
14. Python Certification Training https://www.edureka.co/python
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!
15. Python Certification Training https://www.edureka.co/python
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'
16. Python Certification Training https://www.edureka.co/python
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
17. Python Certification Training https://www.edureka.co/python
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')]
18. Python Certification Training https://www.edureka.co/python
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%
19. Python Certification Training https://www.edureka.co/python
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
20. Python Certification Training https://www.edureka.co/python
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
21. Python Certification Training https://www.edureka.co/python
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
22. Python Certification Training https://www.edureka.co/python
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']
23. Python Certification Training https://www.edureka.co/python
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
24. Python Certification Training https://www.edureka.co/python
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
25. Python Certification Training https://www.edureka.co/python
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
26. Python Certification Training https://www.edureka.co/python
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
27. Python Certification Training https://www.edureka.co/python
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']
28. Python Certification Training https://www.edureka.co/python
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'>
30. Python Certification Training https://www.edureka.co/python
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
31. Python Certification Training https://www.edureka.co/python
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
32. Python Certification Training https://www.edureka.co/python
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
33. Python Certification Training https://www.edureka.co/python
Parameters
Return values
def my_function(x):
return 5 * x
print(my_function(3))
print(my_function(5))
print(my_function(9))
Example
C:UsersMy Name>python
demo_function_return.py
15
25
45
34. Python Certification Training https://www.edureka.co/python
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
36. Python Certification Training https://www.edureka.co/python
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
37. Python Certification Training https://www.edureka.co/python
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
38. Python Certification Training https://www.edureka.co/python
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):
return lambda a : a * n
39. Python Certification Training https://www.edureka.co/python
Why Use Lambda Function?
def myfunc(n):
return lambda a : a * 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