How to write for loops in Python

A for loop is used for iterating over a sequence. This artice shows how to use for loops.

A for loop is used for iterating over a sequence. This can be for example a list, a tuple, a dictionary, a set, a string, or a range object.

#more

To use a for loop we use the for x in sequence syntax.

With the for loop we can execute a set of statements, once for each item in the sequence.

numbers = [1, 2, 3]
for x in numbers:
    print(x)

1
2
3

Loop with the range function¶

To loop over numbers and use the current index, we can use the range function.

for i in range(3):
    print(i)

0
1
2

Range can take only a stop argument, or a start and a stop argument. In the latter case it can also take an optional step argument:

• range(stop)
• range(start, stop)
• range(start, stop, step)

Loop through a String¶

Looping through a string will go over each character.

for x in "python":
    print(x)

p
y
t
h
o
n

The break statement¶

The break statement can be used for an early stopping of the loop before it has looped through all the items. Typically this is applied when a certain condition is met.

values = ["one", "two", "three"]
for value in values:
    print(x)
    if value == "two":
        break

one
two

The continue statement¶

The continue statement is used to skip the current iteration.

values = ["one", "two", "three"]
for value in values:
    if value == "two":
        continue
    print(x)

one
three

Note that here the print statement is applied at the end of each iteration, so after the possible continue statement.

Advanced looping with enumerate¶

With enumerate(x) we can access both the index and the item:

values = ["one", "two", "three"]
for idx, value in enumerate(values):
    print(idx, value)

0 one
1 two
2 three