Using while-break to prevent 'ugly' nested if

main.py

# example nested if, in real life it will be uglier
if a:
    # do some code with a
    if b:
        # do some code with a and b
        if c:
            # do some code with a, b and c
    else:
        print "you must set b"
else:
    print "a is not set, so b no check"

# its better
while True:
    if not a:
        print "a is not set, so b no check"
        break
    # do some code with a
    if not b:
        print "you must set b"
        break
    # do some code with a and b
    if c:
        # do some code with a, b and c