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]]
