Do Loops – For Loops

There are similar small differences in the syntax of do loops in Python. First, they are actually for loops and unless told otherwise will begin with zero. This is a result of Python arrays being a zero-based system, as compared to Fortran, which is a one-based array system. Here is example code is a simple Python for loop with values of i from 0 to 9, which is very similar to the Fortran loop in Do Loops Example 1.

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

Output:

0
1
2
3
4
5
6
7
8
9

Notice again how Python used the colon (:) at the end of the for loop line and when un-indented tells Python we are out of the loop.

The while loop is introduced below and works in the same ways as the Fortran while loop. This loop will continue going until the logical statement is no longer true. Be careful as you might create and infinite loop and your program will never ever, not in a million billion years, end.

a = 5
b = 10
while (a < b):
  print(a)
  a = a + 1