P02: While loops¶
While Loops¶
A while loop is a procedure to repeat a piece of code while some condition is still met.
while loops always have the structure:
while condition:
# Loop contents
While condition is true, execute the code contents.
Repeat until condition is no longer True.
While Loops¶
number = 10
while number >= 0:
print(number)
number = number - 1
10
9
8
7
6
5
4
3
2
1
0
Infinite loops¶
While loops are a great way for beginners to shoot themselves in the foot: it is very easy to introduce a slight bug that causes the while condition to always evaluate to true, and thus the while loop will never stop. When this happens, you have to stop the python kernel/interpreter, and start over. For this reason, you should not use while loops unless you have a very good reason to do so. For-loops are preferable!
Examples of while loops that never end:
number = 10
while number >= 0:
print(number)
number = number - 1
number = 10
while number >= 0:
print(number)
number = number + 1
number = 0
while number <= 0:
print(number)
number = number - 1