一 列表補充 Lists

需要掌握的其它命令

index

Returns the index of the first element with the specified value

count

Returns the number of elements with the specified value

extend

Add the elements of a list (or any iterable), to the end of the current list

reverse

Reverses the order of the list

sort

Sorts the list

二 元組 Tuples

1.定義 Definition

Tuples are written with round brackets, elements in tuples are separated by commas

Notice that you should add a comma in the brackets if there is only one element in a tuple

A tuple is a collection which is ordered and unchangeable.

2.作用 Usage

Tuples are used to store multiple items in a single variable.

3.優先掌握的操作

Similar to the previous list

三 字典 Dictionary

1.定義 Definition

A dictionary is a collection which is unordered, changeable and does not allow duplicates.

Dictionaries are written with curly brackets, and have keys and values,and can be referred to by using the key name.

2.作用 Usage

Dictionaries are used to store data values in key:value pairs.

3.特點 Characteristic

Changeable

可變類型

Unordered

無序

Duplicates Not Allowed

Dictionaries cannot have two items with the same key:

4.數據轉化 Convert

可以將含有嵌套的部分列表轉為字典

5.需要掌握的操作

取值 Access items

You can access the items of a dictionary by referring to its key name, inside square brackets:

The keys() method will return a list of all the keys in the dictionary

通過get取值 Access items by "get"

This method is similar to the previous one, but if the key you input were not in the dictionary, it could return the value "None"

Update

Updates the dictionary with the specified key-value pairs

Setdefault

Returns the value of the specified key. If the key does not exist: insert the key, with the specified value

補充了解

1.深淺拷貝

Shallow copy and Deep copy

# from copy import deepcopy

import copy

?

l = [11, 22, [111, 222]]

new_l = l.copy()

new2_l = copy.deepcopy(l)

l[2][0] = 333

# 改變原列表的字列表中的一個值,觀察新列表的變化

print("原列表", l)

# 淺拷貝得到的列表會隨著原列表而改變

print("淺拷貝新列表", new_l)

# 而深拷貝得到的列表不會改變

print("深拷貝新列表", new2_l)

2.列表為什么沒有find命令

3.hash

A hash is a function that converts one value to another. Hashing data is a common practice in computer science and is used for several different purposes. Examples include cryptography, compression, checksum generation, and data indexing.

Hash算法可以將一個數據轉換為一個標志，這個標志和源數據的每一個字節都有十分緊密的關系。Hash算法還具有一個特點，就是很難找到逆向規律。

具體請見百度百科:

總結

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