csci133ifelif.py

Reference: http://stackoverflow.com/questions/7052393/python-elif-or-new-if
Today when I am reading on the python exercises, I came across one of the exercise program it uses elif (in chapter 10). For a second I am not sure what does it mean because it is called differently. But when I read closely to the source file. It looks like it is trying to replaces some of the other if else statements. Finally I look it up online, I found out it is a little bit more than just if else loops.

def foo(var):
    # Check if var is 5
    if var == 5:
        var = 6
    elif var == 6:
        var = 8
    else:
        var = 10
    return var

def bar(var):
    if var == 5:
        var = 6
    if var == 6:
        var = 8
    if var not in (5, 6):
        var = 10
    return var

print foo(5) # 6
print bar(5) # 8

You can see the exam of foo(5), if the val is 5. Then the rest of them are treated as (else) loop. The elif is a nested else if loop. It is good (maybe) if you want a cleaner looking program, because you don't have the nested else if loops, the indent level is smaller, and faster compare to a sequence of if, if, if statements, because you are not checking explicitly for every single if statement. Note: always try to put the most common condition on the top, so things can check off the 'list of conditions' faster.

For example: If you want to check if a string is English word or not, you would want to check if "isalpha()" or not, and then you start to clean up the letters. So that way, your loop will exist as soon as it knows it contain non-letter characters.