Study notes (14): zero-base mastering Python entry to actual combat-Python operators and simple sentences

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Boolean type Bool: The values ​​are only True and False.

Four arithmetic operations can be performed with numbers.

True=1 False=0

bool() checks whether an object is true or false.

Empty and empty strings are both false

The space is True.

Empty list, empty string, empty dictionary are all false.

Comparison operation: return True if the relationship is established, return False if the relationship is not established.

Normally, the same type is compared.

logic operation:

and：A and B

Short-circuit calculation: first look at whether A is true or false, if it is false, return the A object, if A is true, then return B.

or：A and B

Short-circuit calculation: If the A object is true, then return the A object, if the A object is false, then return the B object.

not: Negate all objects behind not.

Simple statement:

Import module

import module as new_name change the name of the imported module

Import math as shuxue use shuxue instead of math

From module import function Import the specified function from a module.

After from math import pi is introduced, you don't need to write math.pi anymore, you can write pi directly.

From module import function as new_name Import the specified function from a module and change the name.

From module import * Import all the functions under this module. It is discouraged to use, which may cause the same name with some functions in the program.

Assignment statement:

Basic form

Variable = object

Other tricks:

a=1，2，3

This is assembled into tuples.

a,b,c = 1,2,3

a,_,c = 1,2,3, as long as 1 and 3, 2 are not needed. _ Serve as a place.

a, *b = 1,2,3 a=1 b=[2,3]

a= a+1 --> a+=1 Incremental variable.