Python operators

Operators simply do things to values (which, as we have learned, oftentimes live inside variables):

• arithmetic
  • e.g. addition, subtraction, multiplication, division, remainder
• assignment
  • e.g. assignment, increment, decrement
• comparison
  • e.g. equality, inequality, greater than (or equal to), lesser than (or equal to)
• logical
  • e.g. and (all values are true), or (one of the values is true)

Let's have a look some operators...

Arithmetic operators

These operators try to alter values with an integer or float type:

An example of some of the less obvious operators:

x = 14
y = 3

print(x ** y) # 14^3 = 2744
print(x // y) # floor(14/3) = 4
print(x % y) # 2 

# note: 14/3 leaves a remainder of 2

Assignment operators

These operators put values into some named piece of memory (basically the same thing as declaring a variable!) In addition, they may also perform an additional arithmetic operation with a shorter syntax:

x = 2
x += 4 

print(x)
# 6

Note that the second line of the above is equivalent to:

x = x + 4

Other assignment operators also include:

x = 2

x -= 1
print(x)
# 1 
# recall: (2 - 1 == 1)

x *= 8
print(x)
# 8
# recall: (1 * 8 == 8)

x /= 4 
print(x)
# 2
# recall: (8 / 4 == 2)

x %= 1
print(x) 
# 0 
# recall: (2 % 1 == 0)

Comparison operators

When we want to look at two different values, we can use these operators:

x = 3
y = 4 

print(x == y)
# false (x is not "equal" to y)

print (x != y)
# true (x "is not equal" to y)

print(x > y) 
# false (x is not "greater" than y)

print (x < y)
# true (x is "less" than y)

print (x >= y)
# false (x is not "greater than or equal" to y)

print (x <= y)
# true (x is "less than or equal" to y)

Logical operators

When we want to evaluate multiple comparisons or conditions, we can use things like "and" and "or" and "not":

x = 9
y = 15
z = 4

print(x > 3 and y > 10)
# True

print(x < 3 and y > 10)
# False (x is not "less than 3")

print(x > 3 or y > 10)
# True (both are true but only one of them needs to be)

print(x > 3 or y > 10)
# True (only y > 10 needs to e true)

print(not(z > 2))
# False (z is not "not greater than" 2, i.e. it is!)