Control blocks

Python does not use a special character, such as }, to signify the end of a control block such as an if statement. Instead, Python uses indentation to indicate the end of a control block. You define the indentation that governs a block. When your script returns to the original indentation, the block ends. For example, 

max = 5
i = 0
while i <= max:
    square = i**2
    cube = i**3
    print(i, square, cube)
    i = i + 1
print('Loop completed')

When you are using the Python interpreter from the Abaqus/CAE command line interface or if you are running Python from a local Linux or Windows window, the prompt changes to the . . . characters to indicate that you are in a block controlled by indentation.

if, elif, and else
>>> load = 10
>>> if load > 6.75:
...     print 'Reached critical load'
... elif load < 2.75:  
...     print 'Minimal load'
... else:
...     print 'Typical load'
while
>>> load   = 10
>>> length = 3
>>> while load < 1E4:
...     load = load * length
...     print load

Use break to break out of a loop.

>>> while 1:
...     x = raw_input(Enter a number or 0 to quit:')
...     if x == '0':
...         break
...     else:
...         print x

Use continue to skip the rest of the loop and to go to the next iteration.

>>> load   = 10
>>> length = -3
>>> while load < 1E6:  #Continue jumps up here
...     load = load * length
...     if load < 0:
...         continue   #Do not print if negative
...     print load
for

Use a sequence to control the start and the end of for loops. The range() function is an easy way to create a sequence.

>>> for i in range(5):
...     print i
...
0 
1
2
3
4