Loading lesson path
Concept visual
Overview
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.
Print each fruit in a fruit list: fruits = ["apple", "banana", "cherry"] for x in fruits:
print(x)The for loop does not require an indexing variable to set beforehand.
Even strings are iterable objects, they contain a sequence of characters:
Loop through the letters in the word "banana": for x in "banana":
print(x)With the break statement we can stop the loop before it has looped through all the items:
is "banana": fruits = ["apple", "banana", "cherry"] for x in fruits:
print(x)
if x ==
"banana":break
is "banana", but this time the break comes before the print:
fruits = ["apple", "banana", "cherry"]for x in fruits: if x == "banana":
break print(x)With the continue statement we can stop the current iteration of the loop, and continue with the next:
fruits = ["apple", "banana", "cherry"] for x in fruits: if x == "banana":
continue print(x)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)is not the values of 0 to 6, but the values 0 to 5. The range() function defaults to 0 as a starting value, however it is possible to specify the starting value by adding a parameter: range(2, 6), which means values from 2 to 6 (but not including 6):
for x in range(2, 6):
print(x)
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,)
Increment the sequence with 3 (default is 1): for x in range(2, 30, 3):
print(x)The else keyword in a for loop specifies a block of code to be executed when the loop is finished:
Print all numbers from 0 to 5, and print a message when the loop has ended: 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.is 3, and see what happens with the else block:
for x in range(6):
if x == 3: break print(x)
else:
print("Finally finished!")