Operators are the constructs which can manipulate the value of operands.
Consider the expression 4 + 5 = 9. Here, 4 and 5 are called operands and + is called operator.
Types of Operator
Python language supports the following types of operators.
- Arithmetic Operators
- Comparison (Relational) Operators
- Assignment Operators
- Logical Operators
- Bitwise Operators
- Membership Operators
- Identity Operators
Let us have a look on all operators one by one.
Python Arithmetic Operators
Assume variable a holds 10 and variable b holds 20, then −
[ Show Example ]
| Operator | Description | Example |
|---|---|---|
| + Addition | Adds values on either side of the operator. | a + b = 30 |
| - Subtraction | Subtracts right hand operand from left hand operand. | a – b = -10 |
| * Multiplication | Multiplies values on either side of the operator | a * b = 200 |
| / Division | Divides left hand operand by right hand operand | b / a = 2 |
| % Modulus | Divides left hand operand by right hand operand and returns remainder | b % a = 0 |
| ** Exponent | Performs exponential (power) calculation on operators | a**b =10 to the power 20 |
| // | Floor Division - The division of operands where the result is the quotient in which the digits after the decimal point are removed. But if one of the operands is negative, the result is floored, i.e., rounded away from zero (towards negative infinity) − | 9//2 = 4 and 9.0//2.0 = 4.0, -11//3 = -4, -11.0//3 = -4.0 |
Python Comparison Operators
These operators compare the values on either sides of them and decide the relation among them. They are also called Relational operators.
Assume variable a holds 10 and variable b holds 20, then −
[ Show Example ]
| Operator | Description | Example |
|---|---|---|
| == | If the values of two operands are equal, then the condition becomes true. | (a == b) is not true. |
| != | If values of two operands are not equal, then condition becomes true. | (a != b) is true. |
| <> | If values of two operands are not equal, then condition becomes true. | (a <> b) is true. This is similar to != operator. |
| > | If the value of left operand is greater than the value of right operand, then condition becomes true. | (a > b) is not true. |
| < | If the value of left operand is less than the value of right operand, then condition becomes true. | (a < b) is true. |
| >= | If the value of left operand is greater than or equal to the value of right operand, then condition becomes true. | (a >= b) is not true. |
| <= | If the value of left operand is less than or equal to the value of right operand, then condition becomes true. | (a <= b) is true. |
Python Assignment Operators
Assume variable a holds 10 and variable b holds 20, then −
[ Show Example ]
| Operator | Description | Example |
|---|---|---|
| = | Assigns values from right side operands to left side operand | c = a + b assigns value of a + b into c |
| += Add AND | It adds right operand to the left operand and assign the result to left operand | c += a is equivalent to c = c + a |
| -= Subtract AND | It subtracts right operand from the left operand and assign the result to left operand | c -= a is equivalent to c = c - a |
| *= Multiply AND | It multiplies right operand with the left operand and assign the result to left operand | c *= a is equivalent to c = c * a |
| /= Divide AND | It divides left operand with the right operand and assign the result to left operand | c /= a is equivalent to c = c / ac /= a is equivalent to c = c / a |
| %= Modulus AND | It takes modulus using two operands and assign the result to left operand | c %= a is equivalent to c = c % a |
| **= Exponent AND | Performs exponential (power) calculation on operators and assign value to the left operand | c **= a is equivalent to c = c ** a |
| //= Floor Division | It performs floor division on operators and assign value to the left operand | c //= a is equivalent to c = c // a |
Python Bitwise Operators
Bitwise operator works on bits and performs bit by bit operation. Assume if a = 60; and b = 13; Now in binary format they will be as follows −
a = 0011 1100
b = 0000 1101
-----------------
a&b = 0000 1100
a|b = 0011 1101
a^b = 0011 0001
~a = 1100 0011
There are following Bitwise operators supported by Python language
[ Show Example ]
| Operator | Description | Example |
|---|---|---|
| & Binary AND | Operator copies a bit to the result if it exists in both operands | (a & b) (means 0000 1100) |
| | Binary OR | It copies a bit if it exists in either operand. | (a | b) = 61 (means 0011 1101) |
| ^ Binary XOR | It copies the bit if it is set in one operand but not both. | (a ^ b) = 49 (means 0011 0001) |
| ~ Binary Ones Complement | It is unary and has the effect of 'flipping' bits. | (~a ) = -61 (means 1100 0011 in 2's complement form due to a signed binary number. |
| << Binary Left Shift | The left operands value is moved left by the number of bits specified by the right operand. | a << 2 = 240 (means 1111 0000) |
| >> Binary Right Shift | The left operands value is moved right by the number of bits specified by the right operand. | a >> 2 = 15 (means 0000 1111) |
Python Logical Operators
There are following logical operators supported by Python language. Assume variable a holds 10 and variable b holds 20 then
[ Show Example ]
| Operator | Description | Example |
|---|---|---|
| and Logical AND | If both the operands are true then condition becomes true. | (a and b) is true. |
| or Logical OR | If any of the two operands are non-zero then condition becomes true. | (a or b) is true. |
| not Logical NOT | Used to reverse the logical state of its operand. | Not(a and b) is false. |
Python Membership Operators
Python’s membership operators test for membership in a sequence, such as strings, lists, or tuples. There are two membership operators as explained below −
[ Show Example ]
| Operator | Description | Example |
|---|---|---|
| in | Evaluates to true if it finds a variable in the specified sequence and false otherwise. | x in y, here in results in a 1 if x is a member of sequence y. |
| not in | Evaluates to true if it does not finds a variable in the specified sequence and false otherwise. | x not in y, here not in results in a 1 if x is not a member of sequence y. |
Python Identity Operators
Identity operators compare the memory locations of two objects. There are two Identity operators explained below −
[ Show Example ]
| Operator | Description | Example |
|---|---|---|
| is | Evaluates to true if the variables on either side of the operator point to the same object and false otherwise. | x is y, here is results in 1 if id(x) equals id(y). |
| is not | Evaluates to false if the variables on either side of the operator point to the same object and true otherwise. | x is not y, here is not results in 1 if id(x) is not equal to id(y). |
Python Operators Precedence
The following table lists all operators from highest precedence to lowest.
[ Show Example ]
| Sr.No. | Operator & Description |
|---|---|
| 1 |
**
Exponentiation (raise to the power)
|
| 2 |
~ + -
Complement, unary plus and minus (method names for the last two are +@ and -@)
|
| 3 |
* / % //
Multiply, divide, modulo and floor division
|
| 4 |
+ -
Addition and subtraction
|
| 5 |
>> <<
Right and left bitwise shift
|
| 6 |
&
Bitwise 'AND'
|
| 7 |
^ |
Bitwise exclusive `OR' and regular `OR'
|
| 8 |
<= < > >=
Comparison operators
|
| 9 |
<> == !=
Equality operators
|
| 10 |
= %= /= //= -= += *= **=
Assignment operators
|
| 11 |
is is not
Identity operators
|
| 12 |
in not in
Membership operators
|
| 13 |
not or and
Logical operators
|
Python - Decision Making
Decision making is anticipation of conditions occurring while execution of the program and specifying actions taken according to the conditions.
Decision structures evaluate multiple expressions which produce TRUE or FALSE as outcome. You need to determine which action to take and which statements to execute if outcome is TRUE or FALSE otherwise.
Following is the general form of a typical decision making structure found in most of the programming languages −
Python programming language assumes any non-zero and non-null values as TRUE, and if it is either zero or null, then it is assumed as FALSE value.
Python programming language provides following types of decision making statements. Click the following links to check their detail.
| Sr.No. | Statement & Description |
|---|---|
| 1 | if statements
An if statement consists of a boolean expression followed by one or more statements.
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| 2 | if...else statements
An if statement can be followed by an optional else statement, which executes when the boolean expression is FALSE.
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| 3 | nested if statements
You can use one if or else if statement inside another if or else ifstatement(s).
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Let us go through each decision making briefly −
Single Statement Suites
If the suite of an if clause consists only of a single line, it may go on the same line as the header statement.
Here is an example of a one-line if clause −
Live Demo#!/usr/bin/python var = 100 if ( var == 100 ) : print "Value of expression is 100" print "Good bye!"
When the above code is executed, it produces the following result −
Value of expression is 100 Good bye!
Python - Loops
In general, statements are executed sequentially: The first statement in a function is executed first, followed by the second, and so on. There may be a situation when you need to execute a block of code several number of times.
Programming languages provide various control structures that allow for more complicated execution paths.
A loop statement allows us to execute a statement or group of statements multiple times. The following diagram illustrates a loop statement −
Python programming language provides following types of loops to handle looping requirements.
| Sr.No. | Loop Type & Description |
|---|---|
| 1 | while loop
Repeats a statement or group of statements while a given condition is TRUE. It tests the condition before executing the loop body.
|
| 2 | for loop
Executes a sequence of statements multiple times and abbreviates the code that manages the loop variable.
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| 3 | nested loops
You can use one or more loop inside any another while, for or do..while loop.
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Loop Control Statements
Loop control statements change execution from its normal sequence. When execution leaves a scope, all automatic objects that were created in that scope are destroyed.
Python supports the following control statements. Click the following links to check their detail.
Let us go through the loop control statements briefly
| Sr.No. | Control Statement & Description |
|---|---|
| 1 | break statement
Terminates the loop statement and transfers execution to the statement immediately following the loop.
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| 2 | continue statement
Causes the loop to skip the remainder of its body and immediately retest its condition prior to reiterating.
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| 3 | pass statement
The pass statement in Python is used when a statement is required syntactically but you do not want any command or code to execute.
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