For loops

For loops’ are used to iterate (repeat) a certain function x nubers of times.

Example

list_of_cubes = [] #we have an empty list
if __name__ == '__main__':
    for element in some_kind_of_list:
        list_of_cubes.append(element * element * element)
        print(list_of_cubes)

here, we have for every element in the original list multiplied it by itself three times and then cumulatively added the products of three for each of the elements into the fist list.

Infinite loops

Loops can be infinite. To avoid too much time spent waiting for one (e.g. if you had no idea it would be printing unnecessary text), click the button stop on the left side.

Example_2

new_filtered_list = []
big_elements = []
for element in some_kind_of_list:
    if element <= 4:
        new_filtered_list.append(element)
    else:
        big_elements.append(element)

print(new_filtered_list)
print(big_elements)

Example_3 - Range

for i in range(5000):
    print(i)

Using Range function in this case is like saying to Python : give us first 5000 values starting with zero (including zero). Range can be defined either as values leading up to a certain integer (as seen above), mind you that zero is seen as the first number, or as a range across values. e.g.

for i in range(3, 15):
    print(i)

This example would give you only the values in the designated interval. Adding more values between 3 and 15 will not change the outcome. Python won’t however work with more than 3 values defining a range of numbers.

Homework

try for yourself- give us an example of the sum of first 100000 natural numbers

Are you eager to learn more about for loops?

If so, make sure to check these links out and become a pro:

Official Python tips on For loops

Explained in a video + notes

A bit more interactive explanation