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一.Introduction

2024-08-17 11:45:43   221人阅读

1.8.1 Built-in Atomic Data Types

Python has two main built-in numeric classes（内置函数，int 和 float） that implement the integer and floating point data types。

other operation are  remainder operator %(取模运算)，the operator ** is exponentiation(指数运算)

 

python 中的变量 variable 不像C++、java一样，同一个类型的variable能够refer to many different types of data 

 

1.8.2. Built-in Collection Data Types:

Lists, strings, and tuples (tuples 元组)are ordered collections that are very similar in general structure but have specific differences 。

Sets and dictionaries are unordered collections.

类表，字符串和元组是有序的集合，Sets和字典无序集合

1.list，List中object不需要全部相同类型

.

>>> [1,3,True,6.5]
[1, 3, True, 6.5]
>>> myList = [1,3,True,6.5]
>>> myList
[1, 3, True, 6.5]

 

,

>>> myList = [0] * 6
>>> myList
[0, 0, 0, 0, 0, 0]

 list 列表[1,2,3]*3，说的是将此[1,2,3]重新复制3片，与numpy中array，中* 针对数组中每个元素乘以其常数K

import numpy
>>> myList=[1,2,3]
>>> myList *3
[1, 2, 3, 1, 2, 3, 1, 2, 3]
>>> myarray=numpy.array(myList)
>>> myarray
array([1, 2, 3])
>>> myarray*3
array([3, 6, 9])
List列表的操作特性,List 可以进行pop和insert,pop 弹出的是list中最末尾的元素.
remove 操作可以直接删除list中某个值。()__add__()，called it add method，标识符
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2.string:

>>> "David"
‘David‘
>>> myName = "David"
>>> myName[3]技术分享

‘i‘
>>> myName*2
‘DavidDavid‘
>>> len(myName)
5
>>>

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 A major difference between lists and strings is that lists can be modified while strings cannot

list 与string最大不同的点在于List中元素能够进修改，string不能

 3.Tuple ，元组中数据不能被修改的  The difference is that a tuple is immutable, like a string

 myTuple=(1,True,4.98)

>>> myTuple
(1, True, 4.98)
>>> myTuple*3
(1, True, 4.98, 1, True, 4.98, 1, True, 4.98)
>>> myTuple[1]=9

Traceback (most recent call last):
File "<pyshell#17>", line 1, in <module>
myTuple[1]=9
TypeError: ‘tuple‘ object does not support item assignment
>>>

 

4.Set集合，集合中元素不会有重复的

1.set 中元素显示不会按照一定的顺序，会一种unordered方式：

 

{3,6,"cat",4.5,False}
{False, 4.5, 3, 6, ‘cat‘}
>>> mySet = {3,6,"cat",4.5,False}
>>> mySet
{False, 4.5, 3, 6, ‘cat‘}
>>>

 mylist=[1,2,3,1]

>>> set(mylist)
set([1, 2, 3])

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intersection从两个set选择相同的元素setA.intersection(setB)

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 5.词典：dict.items():得到字典中的每一个类型的元素,dict.get(k,0)，从词典中有k得到k，没有的话返回成0

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一.Introduction


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