Python Base Four

35. In python, file operation syntax is similar to c.

open(file,'r',……） //the first parameters is necessary, other is optional ,the second parameters is 'r' by default

if you want to open a file, you can use:

f = open('//Users//wyg_mac//Desktop//Account.txt') //if you don't know the path ,you can drag the file to console

if you want to close file ,you can use:

f.close()

next now that we know how to open file and close file ,but how to read file content.

you can use

f.read(size = -1) //read size buffer, if size not define or  minus ,read next buffer , and return as string

f.readline() //open as write mode, if file exist, append at end

if you want to write content to file ,how to achieve it.

f.wirte(str) // put str write file

f.wirtelines(seq) //

f.tell() // return current position

f.seek(offset,from) //from( if is 0, start position,1 current position 2 end position) offset

such as if i want to create a file demo.txt on desktop and write content whth 'write code change world'

f = open(r'/users/wyg_mac/desktop/demo.txt','w')

f.wirte('write code change world')

f.close()

there are something we need to notice:

if a file not exist , as follow ,it will have error:

f = open(r'/users/wyg_mac/desktop/a.txt')  -> error

if file not exist ,you use follow it will be right:

f = open(r'/users/wyg_mac/desktop/a.txt') -> right

//seventh day to study python

36. In python , os module is base and important.

import os

os.getcwd()  //get current file path

-> '/users/wyg_mac/documents'

os.chdir('/users/wyg_mac/desktop')  //change file path

os.getcwd()

-> '/users/wyg_mac/desktop

os.listdir('/users/wyg_mac/desktop')  //list file dir

-> ['demo.txt', '.DS_Store',]

os.mkdir('/users/wyg_mac/desktop/a')

-> create a file named a

os.mkdir('/users/wyg_mac/desktop/a/b')

-> if file a exist ,create file named b in file a, if a not exist ,will have an error

os.makedirs('/users/wyg_mac/desktop/m/n/o')

-> create file m on desktop , m include n , n include o

if file m/n/o ,o include ttt.txt

os.remove('/users/wyg_mac/desktop/m/m/o/ttt.txt')

-> remove ttt.txt according to path

os.rmdir('/users/wyg_mac/desktop/m/n/o')

-> remove o file , if o contain content , error , if not ,remove it.

os.removedirs('path')

->

os.rename('/users/wyg_mac/desktop/a','/users/wyg_mac/desktop/aaa')

-> change file name

os.system(command)

-> command is shell command, such as os.system('cmd')

os.curdir  //current

-> .

os.pardir //

-> ..

such as:

os.listdir(os.curdir' == os.listdir('.')

os.sep   //current os path sep

-> /

os.name //current os name

-> 'posix'

37. os.path

os.path.bastname('/users/wyg_mac')

-> wyg_name

os.path.dirname('/users/wyg_mac/desktop')

-> users/wyg_mac

os.path.join('/users','wyg_mac','desktop')

-> '/users/wyg_mac/desktop'

os.path.split('/users/wyg_mac/desktop/m/n')

-> ('/users/wyg_mac/desktop/m','n')

os.path.splitext('/users/wyg_mac/desktop/m')

-> ('/users/wyg_mac/desktop/m','')

os.path.splitext('/users/wyg_mac/desktop/m.txt')

-> ('/uses/wyg_mac/desktop/m','.txt')

os.path.getsize('/users/wyg_mac/desktop/m.txt')

-> 35

os.path.getctime()

os.path.getmtime()

os.path.getatime()

os.path.mtime('/users/wyg_mac/desktop/m')

-> 1470748934.0

if you don not understand it ,you can use:

import time

time.localtime(os.path.getmtime('/users/wyg_mac/desktop/m'))

-> time.struct_time(tm_year=2016, tm_mon=8, tm_mday=9, tm_hour=21, tm_min=22, tm_sec=14, tm_wday=1, tm_yday=222, tm_isdst=0

os.path.exists('/users/wyg_mac/desktop/m')

-> True

os.path.isabs()  //if if abs path

os.path.isfile()

os.path.isdir()

os.path.ismount()

os.path.islink()

os.path.samefile(,)

38. pickle module ,you can store data to file and read it

import pickle

my_list = [123, 3.14, 'roy' [1, 3]]

pickle_file = open('my_list.txt', 'wb')

pickle.dump(my_list, pickle_file)

pickle_file.close()

pickle_file = open('my_list.txt','rb')

my_list2 = pickle.load(pickle_file)

print(my_list2)

-> [123, 3.14, 'roy', [1, 3]]