Notes
A single line comment in Python begins with #, for example:
# This is a comment.
print("Hello, World!")
Multi-line comments are enclosed with three single quotation marks'', or three double quotation marks', for example:
'''
This is a multi-line comment with three single quotes
This is a multi-line comment with three single quotes
This is a multi-line comment with three single quotes
'''
print("Hello, World!")
"""
This is a multi-line comment with three double quotes
This is a multi-line comment with three double quotes
This is a multi-line comment with three double quotes
"""
print("Hello, World!")
operator
Arithmetic operator
Compare (relational) operators
Assignment Operators
Logical Operator
Bitwise Operators
member operator
Identity Operator
Operator priority
Python arithmetic operator
+ Plus
- subtraction
* multiplying
/ Division
% Modeling
* power
// take and divide
a = 21
b = 10
c = 0
c = a + b
print("1 - c The value is:", c)
c = a - b
print("2 - c The value is:", c)
c = a * b
print("3 - c The value is:", c)
c = a / b
print("4 - c The value is:", c)
c = a % b
print("5 - c The value is:", c)
# Modify variables a, b, c
a = 2
b = 3
c = a ** b
print("6 - c The value is:", c)
a = 10
b = 5
c = a // b
print("7 - c The value is:", c)
The output of the above example is as follows:
The value of 1 - c is 31
The value of 2 - c is 11
The value of 3 - c is 210
The value of 4 - c is: 2.1
The value of 5 - c is: 1
The value of 6 - c is 8
The value of 7 - c is: 2
Python comparison operator
== Equivalent to - Compare Object Equivalence
!= Not equal - Compare two objects to see if they are not equal
> Is greater than - Return x greater than y
<less than-returns whether x is less than y. All comparison operators return 1 for true and 0 for false. This is equivalent to the special variables True and False, respectively. Note that these variable names are capitalized.
>= greater than or equal to - Returns whether x is greater than or equal to y.
<= less than or equal to - Returns whether x is less than or equal to y.
a = 21
b = 10
c = 0
if ( a == b ):
print ("1 - a Be equal to b")
else:
print ("1 - a Not equal to b")
if ( a != b ):
print ("2 - a Not equal to b")
else:
print ("2 - a Be equal to b")
if ( a < b ):
print ("3 - a less than b")
else:
print ("3 - a Greater than or equal to b")
if ( a > b ):
print ("4 - a greater than b")
else:
print ("4 - a Less than or equal to b")
# Modify the values of variables a and b
a = 5;
b = 20;
if ( a <= b ):
print ("5 - a Less than or equal to b")
else:
print ("5 - a greater than b")
if ( b >= a ):
print ("6 - b Greater than or equal to a")
else:
print ("6 - b less than a")
The output of the above example is as follows:
1 - a is not equal to b
2 - a is not equal to b
3 - a greater than or equal to b
4 - a is greater than b
5 - a is less than or equal to b
6 - b greater than or equal to a
Python assignment operator
= A simple assignment operator c = a + b assigns the result of a + b to C
+= The addition assignment operator c += a is equivalent to c = c + a
-= The subtraction assignment operator c -= a is equivalent to c = c - a
*= Multiplication assignment operator c*= A is equivalent to C = c* a
/= The division assignment operator c/= A is equivalent to c = c / a
%= The modular assignment operator c% = a is equivalent to C = c% = a
**= Power assignment operator c**= A is equivalent to C = c** a
//= The integer division assignment operator c /= A is equivalent to c = c // a
a = 21
b = 10
c = 0
c = a + b
print ("1 - c The value is:", c)
c += a
print ("2 - c The value is:", c)
c *= a
print ("3 - c The value is:", c)
c /= a
print ("4 - c The value is:", c)
c = 2
c %= a
print ("5 - c The value is:", c)
c **= a
print ("6 - c The value is:", c)
c //= a
print ("7 - c The value is:", c)
The output of the above example is as follows:
The value of 1 - c is 31
The value of 2 - c is 52
The value of 3 - c is: 1092
The value of 4 - c is 52.0
The value of 5 - c is: 2
The value of 6 - c is 2097 152
7 - c: 99864
Python logical operator
x and y Boolean "and" - If x is False, x and y returns False, otherwise it returns the calculated value of y. (a and b) Return 20.
Or x or y Boolean "or" - If x is True, it returns the value of x, otherwise it returns the calculated value of y. (a or b) Return 10.
not x Boolean "non" - If x is True, return False. If x is False, it returns True. not(a and b) returns to False
a = 10
b = 20
if ( a and b ):
print ("1 - variable a and b All for true")
else:
print ("1 - variable a and b There is an inaction. true")
if ( a or b ):
print ("2 - variable a and b All for true，Or one of the variables is true")
else:
print ("2 - variable a and b None of them can do it. true")
# Modify the value of variable a
a = 0
if ( a and b ):
print ("3 - variable a and b All for true")
else:
print ("3 - variable a and b There is an inaction. true")
if ( a or b ):
print ("4 - variable a and b All for true，Or one of the variables is true")
else:
print ("4 - variable a and b None of them can do it. true")
if not( a and b ):
print ("5 - variable a and b All for false，Or one of the variables is false")
else:
print ("5 - variable a and b All for true")
The output of the above example is as follows:
1 - Variables a and b are true
2 - Variables a and b are true, or one of them is true
3 - Variables a and b have one not true
4 - Variables a and b are true, or one of them is true
5 - Variables a and b are false, or one of them is false
Python member operator
In. Returns True if a value is found in the specified sequence, or False. X is in the y sequence, if x returns True in the y sequence.
Not in returns True if no value is found in the specified sequence, or False. X is not in the y sequence, if x is not in the y sequence, return True.
a = 10
b = 20
list = [1, 2, 3, 4, 5 ];
if ( a in list ):
print ("1 - variable a In a given list list in")
else:
print ("1 - variable a Not in the given list list in")
if ( b not in list ):
print ("2 - variable b Not in the given list list in")
else:
print ("2 - variable b In a given list list in")
# Modify the value of variable a
a = 2
if ( a in list ):
print ("3 - variable a In a given list list in")
else:
print ("3 - variable a Not in the given list list in")
The output of the above example is as follows:
1 - Variable a is not in the list in the given list
2 - Variable b is not in a given list
3 - Variable a in a given list
Python identity operator
Is to determine whether two identifiers are referenced from an object, x is y, similar to id(x) == id(y), if the same object is referenced, return True, otherwise return False
It is not to determine whether two identifiers are referenced from different objects, similar to ID (a)!= ID (b). If the reference is not the same object, the result True is returned, otherwise False is returned.
a = 20
b = 20
if ( a is b ):
print ("1 - a and b Have the same logo")
else:
print ("1 - a and b No identical identification")
if ( id(a) == id(b) ):
print ("2 - a and b Have the same logo")
else:
print ("2 - a and b No identical identification")
# Modify the value of variable b
b = 30
if ( a is b ):
print ("3 - a and b Have the same logo")
else:
print ("3 - a and b No identical identification")
if ( a is not b ):
print ("4 - a and b No identical identification")
else:
print ("4 - a and b Have the same logo")
The output of the above example is as follows:
1 - a and b have identical identities
2 - a and b have identical identities
3 - a and b do not have the same identification
4 - a and b do not have the same identification
Python Operator Priority
The following table lists all operators from the highest to the lowest priority:
** Index (highest priority)
~+- Bit-by-bit flip, one dollar plus and minus (the last two methods are called +@and-@)
*/%// Multiplication, division, modularization and division
+- Addition and subtraction
"< < Right Shift, Left Shift Operator
& bit `AND'
^| Bit Operator
<= < >= comparison operator
<>==!= equal to operator
=%=/=//=-=+=*= **= assignment operator
Is not an identity operator
in not in member operator
not and or logical operators
a = 20
b = 10
c = 15
d = 5
e = 0
e = (a + b) * c / d #( 30 * 15 ) / 5
print ("(a + b) * c / d The results are as follows:", e)
e = ((a + b) * c) / d # (30 * 15 ) / 5
print ("((a + b) * c) / d The results are as follows:", e)
e = (a + b) * (c / d); # (30) * (15/5)
print ("(a + b) * (c / d) The results are as follows:", e)
e = a + (b * c) / d; # 20 + (150/5)
print ("a + (b * c) / d The results are as follows:", e)
The output of the above example is as follows:
(a + b) * c / d operation results are: 90.0
((a + b) * c) / d operation results are: 90.0
(a + b) * (c / d) operation results are: 90.0
The result of a + (b * c) / d operation is: 50.0