Python Conditions
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.
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".
Indentation
Python relies on indentation, using whitespace, to define scope in the code. Other programming languages often use curly-brackets for this purpose.
Example
Statements on new lines MUST use indentations:
a = 33
b = 200
if b > a:
print("b is greater than a")
Run example »
Example
If statement, without indentation:
a = 33
b = 200
if b > a:
print("b is greater than a")
# you will get an error
Run example »
Elif
The elif keyword is pythons way of saying "if the previous conditions were not true, then do this condition".
Example
a = 33
b = 33
if b > a:
print("b is greater than a")
elif a == b:
print("a and b are equal")
Run example »
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.
Example
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")
Run example »
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".
