3.5.2. Conditional code

Now that we know how to make comparisons, we can control the flow of the program as a result of these comparisons, using if:

if condition:
    perform_task1()
    perform_task2()
    perform_task3()

The if checks if a condition is met. The code block that follows the if statement is executed only if the condition evaluates to True.

WORLD_RECORD = 240
my_score = 236

# Verify if I broke the world record
if my_score > WORLD_RECORD:
    print("I broke the world record!")

This code did nothing, because the condition evaluated to False.

Using the else keyword, it is possible to executes one action if the condition if True and another action if the condition is False:

WORLD_RECORD = 240
my_score = 236

# Verify if I broke the world record
if my_score > WORLD_RECORD:
    print("I broke the world record!")

else:
    print("Nothing to see here.")

Nothing to see here.

It is also possible to evaluate different conditions in a same if series, using elif, which stands for “else if”:

WORLD_RECORD = 240
my_score = 236

# Verify if I broke the world record
if my_score > WORLD_RECORD:
    print("I broke the world record!")

elif my_score == WORLD_RECORD:
    print("I matched the world record!")

else:
    print("Nothing to see here.")

Nothing to see here.

There may be more than one elif in a same series of comparisons:

WORLD_RECORD = 240
my_score = 236

# Verify if I broke the world record
if my_score > WORLD_RECORD:
    print("I broke the world record!")

elif my_score == WORLD_RECORD:
    print("I matched the world record!")

elif my_score > WORLD_RECORD - 5:
    print("I am near the world record!")

else:
    print("Nothing to see here.")

I am near the world record!