In this post is covered the usage of for loop in several situations:

• basic usage
• python for loop skipping step
• looping over list with for loop
• how to loop over dictionary
• how to simulate for loop with while in python

## For loop basic

The most simple usage of for loop in general is to iterate over range of numbers. In this example we iterate over numbers from 0 to 9

``````for i in range(0, 10):
print(i, end=' ,')
``````

result:

0 ,1 ,2 ,3 ,4 ,5 ,6 ,7 ,8 ,9 ,

## For loop skip step

If you want to skip steps in for loop then you can do it by using continue. In the example below we are iterating from 0 to 9 printing only odd numbers. The second example skips exactly 3, 5 and 8 elements:

``````for i in range(0, 10):
if i % 2:
continue
print(i, end=' ,')

for i in range(0, 10):
if i in (3, 5, 8):
continue
print(i, end=' ,')
``````

result:

0, 2 ,4 ,6 ,8 ,
1 ,2 ,4 ,6 ,7 ,9

In some situation could be better to use while loop for skipping steps:

``````i = 1
while i < 10:
if i == 2:
i = 7
print(i, end=' ,')
i += 1
``````

result:

,1 ,7 ,8 ,9 ,

## For loop over list

Looping over list with for is done by using keyword in:

``````people = ["James", "Xie", "Ann", "David"]
for p in people:
print(p, end=' ,')
``````

result:

James ,Xie ,Ann ,David ,

## For loop and dictionary

Iterating over dictionary you can access:

• keys only
• values only
• keys and values
``````score = {'James': 14.1, 'David': 14.3, 'Ann': 15.2, 'Boris': 15.3}

# print only keys
for sc in score:
print(sc, end=' ,')

# print only values
for sc, val in score.items():
print(val, end=' ,')

# print keys and values
for key, value in score.items():
print("key : {0}, value : {1}".format(key, value), end=' ,')

``````

result:

James ,Boris ,Ann ,David ,
15.3 ,15.2 ,14.1 ,14.3 ,
key : James, value : 14.1 ,key : Boris, value : 15.3 ,key : Ann, value : 15.2 ,key : David, value : 14.3 ,

## Simulate for loop with while

Looping over list with for is done by using keyword in:

``````n = 0
while n < 5:
print(n, end=' ,')
n += 1
``````

result:

,0 ,1 ,2 ,3 ,4