Python Loops

In general, the statement of code is executed in sequence from top to bottom. There may be a situation when you need to execute the same block of code several times. Loops are used for this purpose. A loop is a block of statements that are executed until the condition of the loop are fail. Python provides two types of Loop.

while loop
for loop

while loop

Python also has the standard while-loop which work the same as other programming languages like c++ and Java. Let’s see the example of Python while loop.

i = 0
while i < 5:
    print(i)
    i = i + 1

This produces the following result:

For loop

In Python, for loop is used to iterating over the list, tuple, dictionary or string.

vehicle_li = ["car","bus","train"]
for e in vehicle_li:
    print(e)

Output:

car
bus
train

>>> dict = {'a':'red','b':'green','c':'blue'}
>>> for key,val in dict.items():
...     print(f"{key} ==> {val}")
... 
a ==> red
b ==> green
c ==> blue

Range

The range() function is used in for loop to iterate the loop with the specified range. The range(n) function return o to n-1 number. It is not including the last number.

Syntax –

range(start, stop, step)

start: Optional. Default is 0. An integer value specifying the start position.
end: Required. An integer value specifying the end position.
step: Optional.default is 1. An integer value specifying the incrementation.

Examples

>>> for e in range(4):         # end = 4
...     print(e)
... 
0
1
2
3

>>> for e in range(2,6):       # start = 2 & end = 6
... print(e)
... 
2
3
4
5

>>> for e in range(2,10,2):    # start = 2 & end = 10 & step = 2
... print(e)
... 
2
4
6
8

. . .

The break Statement

The break statement is used to terminate the execution of the loop before it has looped through all the items.

>>> for e in range(5):
...     if(e == 3):
...         break
...     print(e)
... 
0
1
2

The continue Statement

The continue statement used to stop the current iteration and continue with the next iteration.

>>> li = [1,2,3,4,5]
>>> for e in li:
...     if(e == 3):
...          continue
...     print(e)
... 
1
2
4
5