Python Path-Basics (i): File processing, lists, tuples, dictionaries, set sets

file processing

File processing mode:

[r] Open in read-only mode (read only) [RB] opens in binary read mode

[W] Open in write-only mode (empty file before writing) [WB] opens in binary write mode

[A] Open in Append mode (append to end of file) [AB] opens in binary append mode

[r+] Open in read-write mode [rb+] in binary read-write mode

[w+] Open in read-write mode [wb+] in binary read-write mode

[A +] open in read-write append mode [ab+] Open in binary read-write append mode

File operations

Open File

f = open (' File path ', ' mode ')

Manipulating files

F.readline ()  # # #仅读取一行数据f. ReadLines () # # #读取所有数据f. Write ()       # # # #写内容

Close File

F.close ()

string                                                                                                                                                                                          

First, the String method

Startswitch: is xxx opening

Endswitch: is XXX end

Strip: Returns a string that removes spaces on both sides

Split: Provides a delimiter to split a string into a list

Join: Specifies a delimiter that is used to concatenate elements in a sequence

Replace: Replaces an element in a string and returns the replaced result (all occurrences)

Second, the method instance operation

Join: Specifies a delimiter that is used to concatenate elements in a sequence

>>>seq = [' 1 ', ' 2 ', ' 3 ', ' 4 ', ' 5 ']>>>b = ' + '    #b为提供的分隔符, if the delimiter is not provided, use a space as a delimiter >>>print (b.join (seq)) 1+2+3+4+5

Replace: Replaces an element in a string and returns the replaced result (all occurrences)

>>>a = ' This was a test ' >>>print (A.replace (' is ', ' si ')) thsi si a test

Split: Provides a delimiter to split a string into a list

>>>a = ' 1+2+3+4+5 ' >>>print (a.split (' + ')) [' 1 ', ' 2 ', ' 3 ', ' 4 ', ' 5 ']

Strip: Returns a string that removes spaces on both sides

>>>a = '  hello,world!   ' >>>print (A.strip ()) hello,world!

sequence                                                                                                                                                                                        

First, the concept

A sequence is a set of sequential elements

There are two types of sequences: tuple (tuple), list

Second, List

Concept:

After the establishment can be deleted and modified

List method:

Append: Appends a new object to the end of the list

Insert: Inserts an object at the specified index location

Reverse: Reverse-store elements in the list

Index: Find a worthwhile index position in the list

Count: Count the number of occurrences of an element in a list

Remove: Remove one of the list's worthy first matches

Extend: Appends multiple values of another list at the end of a list

Sort: Sorting a list

List Method Instances

The corresponding values are listed according to the index:

>>> name_list = [' Zhao ', ' Qian ', ' Sun ']>>> name_list [' Zhao ', ' Qian ', ' Sun ']>>> name_list[0]< c0/> ' Zhao '

Append: Appends a new object to the end of the list

>>> name_list [' Zhao ', ' Qian ', ' Sun ']>>> name_list.append (' li ')   >>> name_list[' Zhao ', ' Qian ', ' sun ', ' Li '

Insert: Inserts an object at the specified index location

>>> Name_list.insert (2, ' a ')  >>> name_list[' Zhao ', ' Qian ', ' A ', ' sun ', ' Li ']

Remove: Remove one of the list's worthy first matches

>>>name_list [' Qian ', ' A ', ' sun ', ' Li ']>>>name_list.remove (' Zhao ') >>> name_list[' Qian ' , ' A ', ' sun ', ' Li '

Count: Count the number of occurrences of an element in a list

>>>name_list[' Zhao ', ' Qian ', ' sun ', ' Li ', ' Zhao ']>>>name_list.count (' Zhao ')   2

Index: Find a worthwhile index position in the list

>>> name_list[' Zhao ', ' Qian ', ' sun ', ' Li ', ' Zhao ']>>> name_list.index (' Qian ')    1

Extend: Appends multiple values of another list at the end of a list

>>>a=[1,2,3]>>>b=[4,5,6]>>>a.extend (b) >>>print (a) [1,2,3,4,5,6]

Intercept when you know the index location

>>> name_list[' Zhao ', ' Qian ', ' sun ', ' Li ', ' Zhou ', ' Wu ', ' Zheng ', ' Wang ']>>>name_list [0:5]         # Intercept 0-5 lines [' Zhao ', ' Qian ', ' sun ', ' Li ', ' Zhou ', ' Wu ']

Intercept without knowing the index position

>>> name_list[' Zhao ', ' Qian ', ' sun ', ' Li ', ' Zhou ', ' Wu ', ' Zheng ', ' Wang ']>>>name_list[name_ List.index (Zhao): Name_list.index (Zhao) +4]  #从zhao开始截取四个包括zhao [' Zhao ', ' Qian ', ' sun ', ' Li ']

Three, meta-group

Concept:

Once established, the elements of the tuple cannot be modified and can only be read

Tuple method

CMP (TUPLE1,TUPLE2): Comparing elements of two tuples

Tuple (a): Convert List A to Narimoto group

To create a tuple:

>>>tuple = (' Zhao ', ' Qian ', ' Sun ')

To delete an entire tuple:

>>> del tuple

Dictionaries                                                                                                                                                                                            

First, the concept

Quickly locate related values, Key,vale. Key is the value of the keys value

Second, the characteristics

Disorder of

Three, the method of the dictionary:

Clear: Clears all items in the dictionary

Items: Returns all items in the dictionary as a list

Copy: Returns a new dictionary of the same key-value pair (shallow copy)

Pop: Specify a build, and then remove this key-value pair from the list

Fromkeys: Creates a new dictionary with the given key, value is None

Update: Updates a dictionary item to another dictionary (the latter replaces the former) method instance

Iv. Examples of dictionary methods

Clear: Make sure all the items in the dictionary

Code: People = {' Zhangsan ': +, ' Lisi ': 18}print (people) print (people.clear ()) Result: {' Lisi ': ' Zhangsan ': 25}none

Copy: Returns a new dictionary of the same key-value pair (shallow copy)

Code: People = {' Zhangsan ': +, ' Lisi ': 18}print (people) print (people.copy ()) Result: {' Lisi ': ' Zhangsan ': 25}{' Lisi ': 18, ' Zhangsan ': 25}

Fromkeys: Creates a new dictionary with the given key, value is None

Code: Dice = {}print (Dict.fromkeys ([' Zhangsan ', ' Lisi ')) Result: {' Lisi ': none, ' Zhangsan ': none}

Items: Returns all items in the dictionary as a list

Code: People = {' name ': ' Zhangsan ', ' age ': '}print ' (People.items ()) Result: [(' Age ', ' ' + '), (' Name ', ' Zhangsan ')]

Pop: Specify a build, and then remove this key-value pair from the list

Code: People = {' name ': ' Zhangsan ', ' age ': '}print ' (people) print (People.pop (' name ')) print (people) Result: {' age ': ' 25 ', ' Name ': ' Zhangsan '}zhangsan{' age ': ' 25 '}

Update: Updates one dictionary item to another dictionary (the latter replaces the former)

Code: People  = {' name ': ' Zhangsan ', ' sarlay ': 6000}people2 = {' name ': ' Zhangsan ', ' Sarlay ': 12000}print (people) print ( People2) Print (People.update (people2)) print (people) Result: {' sarlay ': 6000, ' name ': ' Zhangsan '} {' Sarlay ': 12000, ' name ': ' Zhangsan '}none{' sarlay ': 12000, ' name ': ' Zhangsan '}

Find Value by key

Code: People  = {' name ': ' Zhangsan '}print (people[' name ') ') Result: Zhangsan

Returns all keys in the dictionary

Code dic = {' Tom ': One, ' Sam ': $, ' Lily ': 100}print (Dic.keys ()) results [' Lily ', ' Sam ', ' Tom ']

Returns all the value in the dictionary

Code dic = {' Tom ': One, ' Sam ': $, ' Lily ': 100}print (Dic.values ()) Results [100, 57, 11]

Set Set                                                                                                                                                                                            

First, the concept:

Fast access, can not be repeated, unordered

Two, set Set method:

Add: Adds an element to the collection

Discard: Removes an element from the collection and does not error if the element does not exist

Remove: Removes an element from the collection and an error if the element does not exist

Pop: Randomly deletes an element and returns the element

Union

Difference: Take the difference of two sets

　　

　　

　

　

　　

Python Path-Basics (i): File processing, lists, tuples, dictionaries, set sets