Statements

What is a Statement?

Why Should I Use Statements?

Simple Statements

Compound Statements

If Statements

The if statement can be used to check if an expression is true or false.

With this if statement, I check the equality of 0 against 0.

if 0 == 0:
    print("Indeed")

Will always be true and so print, "Indeed", since 0 is always equal to 0.

Equality is checked on a type basis, as well as on an instance basis. So this if statement, will not run the code inside, as it's comparing an integer and a string.

if 0 == "0":
    print("It's not")

Else

If you want to run some code when the argument is false, you can use else.

if 0 == "0":
    print("Indeed")
else:
    print("I should think not")

Elif

If you want to check something else if the argument is false, you can use an elif. An elif means, "else if".

if 0 == 1:
    print("Indeed")
elif 0 == 0:
    print("It does")
else:
    print("I should think not")

In-Line

The if statement can be used in-line, to set a value to a piece of data depending on if the statement is true or false.

print("Hello" if 0 == 0 else "Bye")

While Statement

The while statement will continue to run the code it contains until the expression it was given is not true.

while 0 == 0:
    print("Hello")

This will print, "Hello" until the program is closed, since 0 always equals 0.

If you want your program to loop forever, it is best to use while True, as it provides good readability.

If you would like your program to loop until a variable is changed, you can use while my_variable, after setting the variable to True, first. This will then run forever, or until you reset the variable to something else. If it is set to something else, the while loop will exit after the rest of the code inside has finished.

my_variable = True
counter = 0

while my_variable:
    print("Hello")
    counter += 1
    
    if counter > 10:
        my_variable = False