Loops

While loops

While loops run the indented code repeatedly while the condition is True:

# i variable as a counteri = 0# loop 5 times when i is 0,1,2,3,4while i < 5:    print(i)    # increment the i counter by 1    i += 1

To skip to the next condition check you can use the continue statement:

i = 0while i < 5:    i += 1    if i == 3:        # continue back up to the chile condition check        continue    print(i)

So this example won't print out 3 as the continue statement will take the flow back to the condition check and then increment i to 4.

To break out a while loop you can use the break statement:

i = 0while i < 5:    print(i)    if i == 3:        # Break out of the while loop and resume executing code below it        break    i += 1

So this example, the last number printed will be 3 and then the while loop is ended.

To run code when the while loop finishes and the condition changes to False, use the else: statement:

i = 0while i < 5:    print(i)    i += 1else:    # This else block executes when the while loop condition becomes false    # It is not executed if the loop is exited via a break statement    print("Natural end of while loop")​# This block executes after the while loop, even if the loop is exited via a break statementprint("After while loop")

The else section will only be ran if the loop naturally gets to the end and the condition changes to False. If the while loop has a break statement ran, then the else section is skipped.

For loops

To loop through 10 iterations from 0 -> 9:

for x in range(10):    print(x)

To loop through 1 -> 10:

for x in range(1, 11):    print(x)

To loop through 2 -> 10, with a 2 step, so every other number:

for x in range(2, 11, 2):    print(x)

You can use the break, continue and else: statements in a for loop, in the same way you can in a while loop.

To loop through a list:

# Sample list of valuesmy_list = [10, 20, 30, 40, 50]​# Iterate through the list and print each valuefor x in my_list:    print(x)

To loop through a list and have the elements index:

# Sample list of valuesmy_list = [10, 20, 30, 40, 50]​# Iterate through the list and print each value and its indexfor i, x in enumerate(my_list):    print(i, x)

The first variable after the for is for the index, and the second is for the value. You need to use the enumerate function to wrap the list.