Python Learning Notes (children under five) deep, shallow copies, files and folders

Python Learning Notes (children under five)

deep copy-shallow copy

a shallow copy is a copy of the reference (copying only the parent object)

a deep copy is a resource copy of an object.

normal replication simply adds a "label" to the same address space, and everything is the same. Change or add, the copied variables will change

.

Examples:

>>> a=[1,2,3]
>>> B=a
>>> A
[1, 2, 3]
>>> b
[1, 2, 3]
>>> a[1]=0
>>> A
[1, 0, 3]
>>> b
[1, 0, 3]
>>> A.append (4)
>>> A
[1, 0, 3, 4]
>>> b
[1, 0, 3, 4]

Shallow Copy

To add Copy module import copy

A shallow copy of the data will not be copied in a separate copy, just a copy of the reference, each element of the ID is the same

Examples:

>>> Import Copy

>>> a=[1,2,[' A ', ' B ', ' C ']
>>> B=copy.copy (a)
>>> b
[1, 2, [' A ', ' B ', ' C ']

>>> ID (a)
48145736L
>>> ID (b)
48123592L
>>> ID (a[0])
30730152L
>>> ID (b[0])
30730152L
>>> a.append (0)
>>> A
[1, 2, [' A ', ' B ', ' C '], 0]
>>> b
[1, 2, [' A ', ' B ', ' C ']
>>> a[2].append (' d ')
>>> A
[1, 2, [' A ', ' B ', ' C ', ' d '], 0]
>>> b
[1, 2, [' A ', ' B ', ' C ', ' d ']]

Deep Copy

simply changing the copy.copy () to a copy.deepcopy () deep copy will put all the data in a single copy

read and write files

can use the Open function. or file Class
Open (name[, mode[, buffering]) file (name[, mode[, buffering])

fo = Open ("/code/1.txt") #使用open函数print Fo.read () Fo.close () f1 = File ("/code/1.txt") #使用file类print F1.read () f1.close () 

mode
R   &NB SP; Read r+   read-write only. Assumption already exists. Writes W   writes from the file pointer position, assuming that it already exists, deleting the original file, and then writing w+  read and write again, assuming that it already exists, delete the original file first. Write a     write again. Append new content to the end of file A +   read and write, append new content at the end of the file B     open binary. Ability to use U   in combination with R, W, a, + to support all line break symbols. "\ r" "\ n"   "\ r \ n"
Sample: Write

#/usr/bin//usr/bin/python2.7#-*-Coding:utf-8-*-fnew = open ('/code/new.txt ', ' W ') fnew.write (' Hello python!! ')  #这时2还没有真正的写到文件里去, just in the buffer. Close or flush before writing to the file Fnew.close ()

File Object Methods

string = Fileobject.read ([size]) reads, starting from the file pointer to read, which allows a size to specify how much string = Fileobject.readline ([size]) reads a row at a time. And the file pointer to the next line list = Fileoject.readlines ([size]) returns a list of characters that hold no Line Fileobject.next () returns the current row, and the file file pointer to the next line is different from ReadLine. ReadLine returns an empty string after all the rows have been read, and next warns
Fileobject.write (String) write
Fileobject.writelines (list) multiple-line writes. Higher efficiency than write, faster

Fileobject.seek (offset, option)

option = 0 Move the file pointer to the file header + offset

option = 1 Move the file pointer to the current position + offset

option = 2 Move the file pointer to the end-at offset

Fileobject.flush () Submit the update. Write the buffer to the file.
Sample: Find

Import REFP = File (' 1.txt ', ' r ') Count = 0for s in Fp.readlines ():      li = Re.findall (' hello ', s)      if Len (li) >0:            Count = Count + len (LI) print "Search" +str (count) + "Hello" fp.close ()

Example: Replace

#-*-coding:utf-8-*-import refp = file (' 1.txt ', ' r+ ') S=fp.read () Fp.seek (0,0) fp.truncate ()    #文件清空fp. Write ( S.replace (' Hello ', ' Hi ')) fp.close ()

OS module

Introduction of OS module import OS
folder Operations through the OS module to create folders, changes, traversal and other create folders (cannot create multi-level folders) Os.mkdir (path [, mode=0777]) Create a folder (can create multi-level folders) Os.makedirs (path [, mode=0777]) Delete folder (cannot delete multilevel folder) Os.rmdir (path) Delete folder (can delete multilevel folder) Os.removedirs (path)
List Folder Os.listdir (path) Get current folder OS.GETCWD () Toggle folder Os.chdir (path)

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Python Learning Notes (children under five) deep, shallow copies, files and folders