Python Learning notes (11) Python Statement (i)

Operators and conditional statements

Arithmetic operators

operator	Description	Example
+	Add-Two objects added	A + B output result 30
-	Minus-get negative numbers or one number minus the other	-B Output Result-10
*	Multiply by two number or return a string that is repeated several times	A * b output result 200
/	Except-X divided by Y	B/A Output Results 2
%	Modulo-Returns the remainder of the division	B% A output result 0
**	Power-Returns the Y power of X	A**b is 10 of 20, output 100000000000000000000
//	Divide-Returns the integer part of the quotient	9//2 output result 4, 9.0//2.0 output 4.0

Comparison operators

operator	Description	Example
==	Equals-compares objects for equality	(A = = B) returns FALSE.
!=	Not equal-compares two objects for unequal	(A! = B) returns TRUE.
<>	Not equal-compares two objects for unequal	(a <> B) returns True. This operator is similar to! =.
>	Greater than-returns whether x is greater than Y	(A > B) returns FALSE.
<	Less-Returns whether x is less than Y. All comparison operators return 1 for true, and return 0 for false. This distinction is equivalent to the special variable true and false.	(A < B) returns TRUE.
>=	Greater than or equal-returns whether X is greater than or equal to Y.	(a >= B) returns FALSE.
<=	Less than or equal-returns whether X is less than or equal to Y.	(a <= B) returns True.

1>>> A = 22>>> B = 23>>> A = =b #判断a, b Two objects are equal, and the returned result is true, indicating that the objects referenced by the two variables are equal4 True5>>> A isb6 True7>>>ID (a), id (b) #a and B refer to the same object8(54354784L, 54354784L)9>>> da ={"Lang":["python", c],"Teacher":"cc"}Ten>>>ImportCopy One>>> db =copy.deepcopy (DA) #深拷贝 A>>>DB -{'Lang': ['python', set ([0, 1, 3, 5, 6])],'Teacher':'cc'} ->>>ID (DA), ID (db) #是不同的两个对象 the(54489976L, 64755912L) ->>> da isDB #判断是否为同一个对象 - False ->>> da = =DB #两个对象相等 + True ->>> da! =DB #两个对象不相等 + False A>>> b =2,3 at>>> a!=b - True ->>> a<>b - True ->>> 321>1234 - False in>>>"321">"1234" - True to>>>

logical operators

　

operator	Logical Expressions	Description	Example
and	X and Y	Boolean "and"-if x is False,x and y returns FALSE, otherwise it returns the computed value of Y.	(A and B) returns 20.
Or	X or Y	Boolean "or"-if X is non-0, it returns the value of x, otherwise it returns the computed value of Y.	(A or B) returns 10.
Not	Not X	Boolean "Non"-returns False if X is True. If X is False, it returns TRUE.	Not (A and B) returns False

BOOL () Determines whether an object is true or False

A and B if a ==true:return bool (B) if a = = False:return false; A is executed first, and if A is true, the result of B is returned. If A is false, it returns false directly

A or b:if a ==true:return true else:return bool (B) First executes a, if a is true, returns True, otherwise returns the bool value of B

1>>> A ="python"2>>> B =[]3>>>BOOL (a)4 True5>>>bool (b)6 False7>>>bool (0)8 False9>>> BOOL (1)Ten True One>>> 4>3 and4<9 A True ->>> 4<3 and4>9 - False the>>> 4>3or4>9 - True ->>> 4<3or4<9 - True +>>> not(4>3) - False +>>> 4>3 and4>9or4<5 #先执行4 >3 is true, then the right side of and is executed, or 4>9 is false, the execution 4<5 to the right of True,and is true, so this returns true A True at>>>

Conditional statements

Review statements

Print, import, and assignment statements

1 Print " Hello World "  #print语句 2HelloWorld3import  math  #import语句  4 >>> a = 2 #赋值语句

Conditional statements

1 ImportRandom #引入随机数模块2A =random.randint (0,100) #随机0到100的整数3 ifA >50:4     Printa #注意: There are four spaces in front of print5     Print "A is bigger than"6 elifA==50:7     Printa8     Print "a is"9 Else:Ten     Printa One     Print "A is smaller than"

Ternary operator

A = y if x else Z means a =y, assign Y this object to a, if X is true, assign Y to a, otherwise assign Z to a

>>> x = 2>>> y = 8>>> a ="python"ifelse"  Web"If X>y assigns Python to a, the Web is assigned a value. >>> a'web'>>>

Python Learning notes (11) Python Statement (i)