一 列表补充 Lists
需要掌握的其它命令
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 元组 Tuples
1.定义 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.优先掌握的操作
Similar to the previous list
三 字典 Dictionary
1.定义 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.特点 Characteristic
Changeable
可变类型
Unordered
无序
Duplicates Not Allowed
Dictionaries cannot have two items with the same key:
4.数据转化 Convert
可以将含有嵌套的部分列表转为字典
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
通过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
补充了解
1.深浅拷贝
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
# 改变原列表的字列表中的一个值,观察新列表的变化
print("原列表", l)
# 浅拷贝得到的列表会随着原列表而改变
print("浅拷贝新列表", new_l)
# 而深拷贝得到的列表不会改变
print("深拷贝新列表", new2_l)
2.列表为什么没有find命令
https://www.cnpython.com/qa/59657
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算法可以将一个数据转换为一个标志，这个标志和源数据的每一个字节都有十分紧密的关系。Hash算法还具有一个特点，就是很难找到逆向规律。
具体请见百度百科: