There are mutable and Immutable types of Pythons built in types Mutable built-in types:
List
Set
Dictionary
Immutable built-in types:
String
Tuple
Number
主要的内置类型：
numerics, sequences, mappings, classes, instances and exceptions
数字、序列、映射、类、实例和异常。
mutable built-in types，可以add, subtract, rearrange their numbers in place。
1.Truth Value Testing
while condition or as operand of the Boolean operations below.
[1]Here are most of the built-in objects considered false:
- constants defined to be false:
NoneandFalse. - zero of any numeric type:
0,0.0,0j,Decimal(0),Fraction(0, 1) - empty sequences and collections:
'',(),[],{},set(),range(0)
and always return one of their operands.)
布尔值True or False：
默认情况下，除非一个对象的__bool__()方法返回的是False,__len__()方法返回值为0，其他情况下的对象默认返回的bool值为True.
下面是常见的内置对象被默认为False的情况：
- None 或 False
- 0值
- 空值，空集合等
2.Boolean Operations--and,or,not
These are the Boolean operations, ordered by ascending priority:
| Operation | Result | Notes |
|---|---|---|
x or y |
if x is false, then y, else x | (1) |
x and y |
if x is false, then x, else y | (2) |
not x |
if x is false, then True, else False
|
(3) |
Notes:
- This is a short-circuit operator, so it only evaluates the second argument if the first one is false.
- This is a short-circuit operator, so it only evaluates the second argument if the first one is true.
-
nothas a lower priority than non-Boolean operators, sonot a == bis interpreted asnot (a == b), anda == not bis a syntax error.
and so on...