Python Operators#
Python can be used like a calculator. Simply type in expressions to get them evaluated.
What are operators in python?
Operators are special symbols in Python that carry out arithmetic or logical computation. The value that the operator operates on is called the operand.
For example:
>>>6+3
9
Here, + is the operator that performs addition. 2 and 3 are the operands and 5 is the output of the operation.
6+3
9
1. Arithmatic Operators#
Arithmetic operators are used to perform mathematical operations like addition, subtraction, multiplication etc.
Symbol |
Task Performed |
Meaning |
Example |
|---|---|---|---|
|
Addition |
add two operands or unary plus |
x + y or +2 |
|
Subtraction |
substract right operand from the left or unary minus |
x - y or -2 |
|
Multiplication |
Multiply two operands |
x * y |
|
Division |
Divide left operand by the right one (always results into float) |
x / y |
|
Modulus (remainder) |
remainder of the division of left operand by the right |
x % y (remainder of x/y) |
|
Integer/Floor division |
division that results into whole number adjusted to the left in the number line |
x // y |
|
Exponentiation (power) |
left operand raised to the power of right |
x ** y (x to the power y) |
As expected these operations generally promote to the most general type of any of the numbers involved i.e. int -> float -> complex.
Example : Arithmetic operators in Python#
print('Addition: ', 1 + 2)
print('Subtraction: ', 2 - 1)
print('Multiplication: ', 2 * 3)
print ('Division: ', 4 / 2) # Division in python gives floating number
print('Division: ', 6 / 2)
print('Division: ', 7 / 2)
print('Division without the remainder: ', 7 // 2) # gives without the floating number or without the remaining
print('Modulus: ', 3 % 2) # Gives the remainder
print ('Division without the remainder: ',7 // 3)
print('Exponential: ', 3 ** 2) # it means 3 * 3
Addition: 3
Subtraction: 1
Multiplication: 6
Division: 2.0
Division: 3.0
Division: 3.5
Division without the remainder: 3
Modulus: 1
Division without the remainder: 2
Exponential: 9
x = 16
y = 3
print('x + y =',x+y) # 19
print('x - y =',x-y) # 13
print('x * y =',x*y) # 48
print('x / y =',x/y) # 5.333
print('x // y =',x//y) # 519
x + y = 19
x - y = 13
x * y = 48
x / y = 5.333333333333333
x // y = 5
1+2+3
6
7-1
6
6 * (3+0j) * 1.0
(18+0j)
5/6
0.8333333333333334
In many languages (and older versions of python) \(\frac{1}{2}=0\) (truncated division). In Python 3 this behaviour is captured by a separate operator that rounds down: (i.e., a // b\(=\lfloor \frac{a}{b}\rfloor\))
5//6.0
0.0
15%10
5
3 ** 2 # it means 3 * 3
9
Python natively allows (nearly) infinite length integers while floating point numbers are double precision numbers:
22**600
28418980453852622603883856494709731311218158362293224700445543940796643776911788129508577246309929258069598467896008287596053863082109746801947722280783720032649818198464452375358348619120021135797251857019557032565638659667745421115194468559021541269027438746788486392649581405327516658718317011453858465218779880972140612551504149701082164179367484198570734230003528355826545644223794779911723917115845213739921327820409005460708547942445234906498880588411276755120002108963510955276534630522965966177951626038063994937181228938844252668098515385045718428663547788122173798704717510979319749834083419004355222012043715855123615249682039587844431246269017612728291710718821388840627277407189863509789929339102406655115786899696829902032282666983426897111750208839152830573688512831984602085360572485861376
22.0**600
---------------------------------------------------------------------------
OverflowError Traceback (most recent call last)
<ipython-input-12-bfc5aa62a0ff> in <module>
----> 1 22.0**600
OverflowError: (34, 'Result too large')
Comparison/Relational operators#
Comparison operators are used to compare values. It either returns True or False according to the condition.
Symbol |
Task Performed |
Meaning |
Example |
|---|---|---|---|
|
greater than |
True if left operand is greater than the right |
x > y |
|
less than |
True if left operand is less than the right |
x < y |
|
equal to |
True if both operands are equal |
x == y |
|
not equal to |
True if both operands are not equal |
x != y |
|
greater than or equal to |
True if left operand is greater than or equal to the right |
x >= y |
|
less than or equal to |
True if left operand is less than or equal to the right |
x <= y |
Note the difference between == (equality test) and = (assignment)
Example : Comparison operators in Python#
print(6 > 3) # True, because 3 is greater than 2
print(6 >= 3) # True, because 3 is greater than 2
print(6 < 3) # False, because 3 is greater than 2
print(3 < 6) # True, because 2 is less than 3
print(3 <= 6) # True, because 2 is less than 3
print(6 == 3) # False, because 3 is not equal to 2
print(6 != 3) # True, because 3 is not equal to 2
print(len("apple") == len("avocado")) # False
print(len("apple") != len("avocado")) # True
print(len("apple") < len("avocado")) # True
print(len("banana") != len("orange")) # False
print(len("banana") == len("orange")) # True
print(len("tomato") == len("potato")) # True
print(len("python") > len("coding")) # False
True
True
False
True
True
False
True
False
True
True
False
True
True
False
x = 30
y = 22
print('x > y is',x>y) # False
print('x < y is',x<y) # True
print('x >= y is',x>=y) # False
print('x <= y is',x<=y) # True
x > y is True
x < y is False
x >= y is True
x <= y is False
z = 3 # 3 is assign to variable z
z == 3 # 3 is equal to z
True
z > 3
False
Comparisons can also be chained in the mathematically obvious way. The following will work as expected in Python (but not in other languages like C/C++):
0.5 < z <= 1 # z == 3
False
Logical/Boolean operators#
Logical operators are the and, or, not operators.
Symbol |
Meaning |
Example |
|---|---|---|
|
True if both the operands are true |
x and y |
|
True if either of the operand is true |
x or y |
|
True if operand are false (complements the operand) |
not x |
Example : Logical operators in Python#
print('True == True: ', True == True)
print('True == False: ', True == False)
print('False == False:', False == False)
print('True and True: ', True and True)
print('True or False:', True or False)
True == True: True
True == False: False
False == False: True
True and True: True
True or False: True
# Another way comparison
print('1 is 1', 1 is 1) # True - because the data values are the same
print('1 is not 2', 1 is not 2) # True - because 1 is not 2
print('A in Milaan', 'A' in 'Milaan') # True - A found in the string
print('B in Milaan', 'B' in 'Milaan') # False - there is no uppercase B
print('python' in 'python is fun') # True - because coding for all has the word coding
print('a in an:', 'a' in 'an') # True
print('27 is 3 ** 3:', 27 is 3**3) # True
1 is 1 True
1 is not 2 True
A in Milaan False
B in Milaan False
True
a in an: True
27 is 3 ** 3: True
<>:3: SyntaxWarning: "is" with a literal. Did you mean "=="?
<>:4: SyntaxWarning: "is not" with a literal. Did you mean "!="?
<>:9: SyntaxWarning: "is" with a literal. Did you mean "=="?
<>:3: SyntaxWarning: "is" with a literal. Did you mean "=="?
<>:4: SyntaxWarning: "is not" with a literal. Did you mean "!="?
<>:9: SyntaxWarning: "is" with a literal. Did you mean "=="?
<ipython-input-19-7c9145eb11e9>:3: SyntaxWarning: "is" with a literal. Did you mean "=="?
print('1 is 1', 1 is 1) # True - because the data values are the same
<ipython-input-19-7c9145eb11e9>:4: SyntaxWarning: "is not" with a literal. Did you mean "!="?
print('1 is not 2', 1 is not 2) # True - because 1 is not 2
<ipython-input-19-7c9145eb11e9>:9: SyntaxWarning: "is" with a literal. Did you mean "=="?
print('27 is 3 ** 3:', 27 is 3**3) # True
print(6 > 3 and 5 > 3) # True - because both statements are true
print(6 > 3 and 5 < 3) # False - because the second statement is false
print(6 < 3 and 5 < 3) # False - because both statements are false
print(6 > 3 or 5 > 3) # True - because both statements are true
print(6 > 3 or 5 < 3) # True - because one of the statement is true
print(6 < 3 or 5 < 3) # False - because both statements are false
print(not 6 > 3) # False - because 6 > 3 is true, then not True gives False
print(not True) # False - Negation, the not operator turns true to false
print(not False) # True
print(not not True) # True
print(not not False) # False
True
False
False
True
True
False
False
False
True
True
False
x = True
y = False
print('x and y is',x and y) # False
print('x or y is',x or y) # True
print('not x is',not x) # False
x and y is False
x or y is True
not x is False
True and (not(not False)) or (True and (not True)) # What will be output?
# True and (not(True)) or (True and (False))
# True and False or (False)
# False or False
# False
False
Bitwise operators#
Bitwise operators act on operands as if they were string of binary digits. It operates bit by bit, hence the name.
For example: 2 is 10 in binary and 7 is 111.
In the table below: Let x = 10 (0000 1010 in binary) and y = 4 (0000 0100 in binary)
Operator |
Meaning |
Symbol |
Task Performed |
Example |
|---|---|---|---|---|
|
Logical and |
|
Bitwise And |
x & y = 0 ( |
|
Logical or |
\(\mid\) |
Bitwise OR |
x | y = 14 ( |
|
Not |
|
Bitwise NOT |
~x = -11 ( |
|
|
|
Bitwise XOR |
x ^ y = 14 ( |
|
|
|
Bitwise right shift |
x >> 2 = 2 ( |
|
|
|
Bitwise left shift |
x << 2 = 40 ( |
a = 2 #binary: 0010
b = 3 #binary: 0011
print('a & b =',a & b,"=",bin(a&b))
a & b = 2 = 0b10
5 >> 1
# 0 ➡ 0000 0101
# 0000 0010
# 0010 is 2 in decimal
2
Explanation:
0000 0101 -> 5 (5 is 0101 in binary)
Shifting the digits by 1 to the right and zero padding that will be: 0 ➡ 0000 0101 = 0000 0010
0000 0010 -> 2
5 << 1
# 0000 0101 ⬅ 0
# 0000 1010
# 1010 is 10 in decimal
10
Explanation:
0000 0101 -> 5
Shifting the digits by 1 to the left and zero padding will be: 0000 0101 ⬅ 0 = 0000 1010
0000 1010 -> 10
6 >> 2 # What will be output???
1
print(not (True and False), "==", not True or not False)
# TRUE == True
True == True
print (False and (not False) or (False and True), "==",not (True and (not False) or (not True)))
False == False
Assignment operators#
Assignment operators are used in Python to assign values to variables.
a = 5 is a simple assignment operator that assigns the value 5 on the right to the variable a on the left.
There are various compound operators in Python like a += 5 that adds to the variable and later assigns the same. It is equivalent to a = a + 5.
Symbol |
Example |
Equivalent to |
|---|---|---|
|
x = 5 |
x = 5 |
|
x += 5 |
x = x + 5 |
|
x -= 5 |
x = x - 5 |
|
x *= 5 |
x = x * 5 |
|
x /= 5 |
x = x / 5 |
|
x %= 5 |
x = x % 5 |
|
x //= 5 |
x = x // 5 |
|
x **= 5 |
x = x ** 5 |
|
x &= 5 |
x = x & 5 |
|
x |= 5 |
x = x | 5 |
|
x ^= 5 |
x = x ^ 5 |
|
x >>= 5 |
x = x >> 5 |
|
x <<= 5 |
x = x << 5 |
The binary operators can be combined with assignment to modify a variable value. For example:
x = 1
x += 2 # add 2 to x
print("x is",x)
x <<= 2 # left shift by 2 (equivalent to x *= 4)
print('x is',x)
x **= 2 # x := x^2
print('x is',x)
x is 3
x is 12
x is 144
Special operators#
Python language offers some special types of operators like the identity operator or the membership operator. They are described below with examples.
1. Identity operators#
is and is not are the identity operators in Python. They are used to check if two values (or variables) are located on the same part of the memory. Two variables that are equal does not imply that they are identical.
Symbol |
Meaning |
Example |
|---|---|---|
|
True if the operands are identical (refer to the same object) |
x is True |
|
True if the operands are not identical (do not refer to the same object) |
x is not True |
Example : Identity operators in Python#
x1 = 6
y1 = 6
x2 = 'Hello'
y2 = 'Hello'
x3 = [1,2,3] # list
y3 = [1,2,3] # list
# Output: False
print(x1 is not y1)
# Output: True
print(x2 is y2)
# Output: False because two list [] can never be equal
print(x3 is y3)
False
True
False
Explanation:
Here, we see that x1 and y1 are integers of same values, so they are equal as well as identical. Same is the case with x2 and y2 (strings).
But x3 and y3 are list. They are equal but not identical. It is because interpreter locates them separately in memory although they are equal.
2. Membership operators#
in and not in are the membership operators in Python. They are used to test whether a value or variable is found in a sequence (string, list, tuple, set and dictionary).
In a dictionary we can only test for presence of key, not the value.
Symbol |
Meaning |
Example |
|---|---|---|
|
True if value/variable is found in sequence |
5 in x |
|
True if value/variable is not found in sequence |
5 not in x |
Example : Membership operators in Python#
x = 'Hello world'
y = {1:'a',2:'b'} # dictionary 1 is key and 'a' is element. So we access element without its key.
# Output: True
print('H' in x) # Do we have 'H' in 'Hello World' ?
# Output: True
print('hello' not in x) # Do we have 'hello' in 'Hello World' ?
# Output: True
print(1 in y)
# Output: False because we cannot identify 'a' without its key hence it is Flase.
print('a' in y)
True
True
True
False
Explanation:
Here, ‘H’ is in x but ‘hello’ is not present in x (remember, Python is case sensitive). Similary, 1 is key and ‘a’ is the value in dictionary y. Hence, 'a'in y returns False.