PYTHON: For Loops

Question

Hey guys,

I am fairly new to python and have just completed the "For loops" lesson. However, I can't seem to get my head around it! Could someone please explain the following in *simple words*???

def print_nums(x):
for i in range(x):
print(i)
return
print_nums(10)

I understand the function however am left wondering what is the I? I know it is a variable but how does this work in the range?

Thanks in advance! 😁

Answer 1

The i is known as a dummy variable. It's role is to take on all the values in a list.
Range creates a list from 0 to x. Thus i goes from 0 to x, one iteration at a time.

Answer 2

In this structure:

for counter in iterable:
pass

values from iterable are copied into counter in each iteration. So here we have 0, 1, 2, ..., 10 for i during run.

Answer 3

First of all, the "return" will make the loop stop when it is reached. So, that loop will only output "0".

If I´m not mistaken, the var i is an integer. It is needed because the loop needs to keep count of the amount of iterations it has performed.

def print_nums(x): // x will be the last integer, defined when you call the func
for i in range(x): // i is a new integer, starting at 0. It will run until it reaches x
print(i) // prints value of i.
return // Ends the loop no matter the condition. Do not use unless you want to stop the loop.

For example:

def print_nums(x):
for i in range(x):
print(i) // I deleted "return"
print_nums(3)

Will output

0
1
2

It will not print 3, because by the time it reaches 3, the loop stops, and the print functions comes AFTER the condition check (for i in range (3))

Answer 4

Thanks lads, think I understand it now!