Where is this text coming from?

Question

When I run the code

with open('file.txt') as file:
line_number = 1
for line in file:
print('{}: {}'.format(line_number, line.rstrip()))
line_number += 1

Python outputs
1: This is line one.
2: This is line two.
3: Finally, we are on the third and last line of the file.
How does it know what to say?! I never told it to print a string saying "This is line one". Also, why does it stop at three? Any help would be appreciated, thanks!

Answer 1

Your code loads a text file and loops through the lines and prints them.