Python Loops
Python has two primitive loop commands:
while loops
for loops
The while Loop
With the while loop we can execute a set of statements as long as a condition
is true.
Example
Print i as long as i is less than 6:
i = 1
while i < 6:
print(i)
i += 1
Note: remember to increment i, or else the loop will continue forever.
The while loop requires relevant variables to be ready, in this example we need
to define an indexing variable, i, which we set to 1.
The break Statement
With the break statement we can stop the loop even if the while condition is
true:
Example
Exit the loop when i is 3:
i = 1
while i < 6:
, print(i)
if i == 3:
break
i += 1
The continue Statement
With the continue statement we can stop the current iteration, and continue
with the next:
Example
Continue to the next iteration if i is 3:
i = 0
while i < 6:
i += 1
if i == 3:
continue
print(i)
The else Statement
With the else statement we can run a block of code once when the condition no
longer is true:
Example
Print a message once the condition is false:
i = 1
while i < 6:
print(i)
i += 1
else:
print("i is no longer less than 6")
Try it Yourself »
, Python 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.
Example
Print each fruit in a fruit list:
fruits = ["apple", "banana", "cherry"]
for x in fruits:
print(x)
Try it Yourself »
The for loop does not require an indexing variable to set beforehand.
Looping Through a String
Even strings are iterable objects, they contain a sequence of characters:
Example
Loop through the letters in the word "banana":
for x in "banana":
print(x)
Try it Yourself »
The break Statement
Python has two primitive loop commands:
while loops
for loops
The while Loop
With the while loop we can execute a set of statements as long as a condition
is true.
Example
Print i as long as i is less than 6:
i = 1
while i < 6:
print(i)
i += 1
Note: remember to increment i, or else the loop will continue forever.
The while loop requires relevant variables to be ready, in this example we need
to define an indexing variable, i, which we set to 1.
The break Statement
With the break statement we can stop the loop even if the while condition is
true:
Example
Exit the loop when i is 3:
i = 1
while i < 6:
, print(i)
if i == 3:
break
i += 1
The continue Statement
With the continue statement we can stop the current iteration, and continue
with the next:
Example
Continue to the next iteration if i is 3:
i = 0
while i < 6:
i += 1
if i == 3:
continue
print(i)
The else Statement
With the else statement we can run a block of code once when the condition no
longer is true:
Example
Print a message once the condition is false:
i = 1
while i < 6:
print(i)
i += 1
else:
print("i is no longer less than 6")
Try it Yourself »
, Python 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.
Example
Print each fruit in a fruit list:
fruits = ["apple", "banana", "cherry"]
for x in fruits:
print(x)
Try it Yourself »
The for loop does not require an indexing variable to set beforehand.
Looping Through a String
Even strings are iterable objects, they contain a sequence of characters:
Example
Loop through the letters in the word "banana":
for x in "banana":
print(x)
Try it Yourself »
The break Statement
