For Loops

A for loop is used for iterating over a sequence (that is either a list, a tuple, a dictionary, a set, or a string).

This is less like the for keyword in other programming languages, and works more like an iterator method as found in other object-orientated programming languages.

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

fruits = ["apple", "banana", "cherry"]
for x in fruits:
  print(x)

Looping Through a String

for x in "banana":
  print(x)
Output :
b
a
n
a
n
a

The break Statement

With the break statement we can stop the loop before it has looped through all the items:

fruits = ["apple", "banana", "cherry"]
for x in fruits:
  print(x)
  if x == "banana":
    break

fruits = ["apple", "banana", "cherry"]
for x in fruits:
  if x == "banana":
    break
  print(x)

The continue Statement

fruits = ["apple", "banana", "cherry"]
for x in fruits:
  if x == "banana":
    continue
  print(x)

The range() Function

To loop through a set of code a specified number of times, we can use the range() function,

The range() function returns a sequence of numbers, starting from 0 by default, and increments by 1 (by default), and ends at a specified number.

for x in range(6):
  print(x)
Output:
0
1
2
3
4
5

The range() function defaults to increment the sequence by 1, however it is possible to specify the increment value by adding a third parameter: range(2, 30, 3):

range(start, end, step)

Else in For Loop

The else keyword in a for loop specifies a block of code to be executed when the loop is finished:

for x in range(6):
  print(x)
else:
  print("Finally finished!")

The else block will NOT be executed if the loop is stopped by a break statement.

Nested Loops

A nested loop is a loop inside a loop.

The "inner loop" will be executed one time for each iteration of the "outer loop":

adj = ["red", "big", "tasty"]
fruits = ["apple", "banana", "cherry"]

for x in adj:
  for y in fruits:
    print(x, y)

The pass Statement

for loops cannot be empty, but if you for some reason have a for loop with no content, put in the pass statement to avoid getting an error.

for x in [0, 1, 2]:
  pass

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