Python - For Loop

The for loop

The for loop in Python is used to iterate over a given sequence and executes a set of statements for each element in the sequence. A sequence can be any data structure like list, tuple, set, string, dictionary and range iterables etc.

Syntax

for iterating_var in sequence:
    statements

Flow Diagram:

For loop over a range:

In the example below, for loop is used over a given range.

print("#Result 1:")
for i in range(4):
  print(i, i * 2)

print("\n#Result 2:")
for j in range(2, 6):
  print(j, j ** 2)

print("\n#Result 3:")
for k in range(10, 2, -2):
  print(k)

The output of the above code will be:

#Result 1:
0 0
1 2
2 4
3 6

#Result 2:
2 4
3 9
4 16
5 25

#Result 3:
10
8
6
4

For loop over List

In the example below, for loop is used over a list to access its elements.

colors = ['Red', 'Blue', 'Green']
for x in colors:
  print(x)

The output of the above code will be:

Red
Blue
Green

For loop over Tuple

In the example below, for loop is used over a tuple to access its elements.

days = ('Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday')
for day in days:
  print(day)

The output of the above code will be:

Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday

For loop over Set

The example below describes how to use a for loop over a set to access its elements.

numbers = {100, 200, 300, 400, 500}
for i in numbers:
  print(i)

The output of the above code will be:

400
100
500
200
300

For loop over String

As discussed earlier, a for loop can be used to access characters of a given string.

word = 'python'
for letter in word:
  print(letter)

The output of the above code will be:

p
y
t
h
o
n

For loop over Dictionary

In the same way, a for loop can be used to access key-value pairs of a given dictionary.

dict = {
  'year': '2000',
  'month': 'March',
  'date': 15
}

print("#Result 1:")
for day in dict:
  print(day)

print("\n#Result 2:")
for day, value in dict.items():
  print(day,value)

The output of the above code will be:

#Result 1:
year
month
date

#Result 2:
year 2000
month March
date 15