Python Conditions and If statements

Python supports the usual logical conditions from mathematics:

• Equals: a == b
• Not Equals: a != b
• Less than: a < b
• Less than or equal to: a <= b
• Greater than: a > b
• Greater than or equal to: a >= b

These conditions can be used in several ways, most commonly in “if statements” and loops.

An “if statement” is written by using the if keyword.

Example

If statement:

a = 33
b = 200
if b > a:
  print("b is greater than a")

Output

In this example we use two variables, a and b, which are used as part of the if statement to test whether b is greater than a. As a is 33, and b is 200, we know that 200 is greater than 33, and so we print to screen that “b is greater than a”.

Elif

The elif keyword is pythons way of saying “if the previous conditions were not true, then try this condition”.

a = 33
b = 33
if b > a:
  print("b is greater than a")
elif a == b:
  print("a and b are equal")

Output

In this example a is equal to b, so the first condition is not true, but the elif condition is true, so we print to screen that “a and b are equal”.

Else

The else keyword catches anything which isn’t caught by the preceding conditions.

a = 200
b = 33
if b > a:
  print("b is greater than a")
elif a == b:
  print("a and b are equal")
else:
  print("a is greater than b")

Output

In this example a is greater to b, so the first condition is not true, also the elif condition is not true, so we go to the else condition and print to screen that “a is greater than b“.