1 #!/usr/bin/env python
  2 # -*- coding:utf-8 -*-
  3 # Author:woshinidaye
  4 
  5 #讀檔案
  6 '''
  7 read() 每次讀取整個檔案，它通常用於將檔案內容放到一個字串變數中。如果檔案大於可用記憶體，為了保險起見，可以反覆呼叫read(size)方法，每次最多讀取size個位元組的內容。
  8 readlines() 之間的差異是後者一次讀取整個檔案，象 .read() 一樣。.readlines() 自動將檔案內容分析成一個行的列表，該列表可以由 Python 的 for ... in ... 結構進行處理。
 
  9 readline() 每次只讀取一行，通常比readlines() 慢得多。僅當沒有足夠記憶體可以一次讀取整個檔案時，才應該使用 readline()。
 10 file = open('user_pwd.txt','r') #r文字檔案。rb,表示二進位制檔案
 11 print(file.read())#讀取整個檔案
 12 print(file.read(2))
 13 print(file.readline())
 14 stu1 123
 15 print(file.readline(1))
 16 print(file.readline(10))
 17 readline是一行一行讀取
 
 18 print(file.readlines())#自動將檔案給到列表裡面，但是三種方式都有換行符，艹了
 19 
 20 為了保障檔案呼叫以後被正確關閉，需要通過try....finally來完成
 21 '''
 22 
 23 '''
 24 try:                #try/finally
 25     file = open('user_pwd.txt','r')
 26     print(file.read())
 27 finally:
 28     if file:
 29         file.close()
 30 '''
 31 
 32 '''
 33
 
 try....finally比較麻煩，可以使用with命令完成
 34 '''
 35 
 36 '''
 37 with open('user_pwd.txt','r') as file:
 38     print(file.read())
 39 '''
 40 
 41 #readline:讀取一行，以文字形式，2就代表前兩列
 42 '''
 43 with open('user_pwd.txt','r') as file:
 44     print(file.readline())
 45 with open('user_pwd.txt','r',encoding='utf-8') as file:
 46     print(file.readline(2)) 
 47 '''
 48 
 49 #readlines:以列表的形式讀取，2就表示 0 1 兩個元素
 50 
 51 '''
 52 with open('user_pwd.txt','r') as file:
 53     print(file.readlines())
 54 with open('user_pwd.txt','r') as file:
 55     print(file.readlines(2))
 56 '''
 57 #['stu1     123\n', 'stu2     123\n', 'stu3     123\n', 'stu4     123']
 58 #['stu1     123\n']
 59 #三種讀取方式都有換行符，另外兩種看不到是因為print認為是換行，所以不是\n
 60 
 61 '''
 62 with open('user_pwd.txt','r') as file:
 63     list = file.readlines()
 64 #去除換行符
 65 for i in range(0,len(list)):
 66     list[i] = list[i].strip('\n')
 67     print(list)
 68 '''
 69 
 70 #寫檔案   w:寫文字檔案，wb，寫二進位制檔案
 71 '''
 72 with open('user_pwd.txt','w') as file:
 73     file.write('stu05    123')
 74 with open('user_pwd.txt','r') as read_file:
 75     print(read_file.read())
 76 '''
 77 #直接用w,若沒有檔案，建立一個新檔案，然後寫新文字進去；若檔案存在，清空以後，寫入文字檔案；
 78 #直接可以用a,不過需要注意格式！
 79 '''
 80 with open('user_pwd.txt','a') as file:
 81     file.write('stu06    123')
 82 with open('user_pwd.txt','r') as read_file:
 83     print(read_file.read())
 84 '''
 85 
 86 '''
 87 with open('user_pwd.txt','w') as file :
 88     file.writelines(['1','2','3'])
 89 with open('user_pwd.txt','r') as read_file:
 90     print(read_file.read())
 91     #結果是123
 92 
 93 with open('user_pwd.txt','w') as file :
 94     file.writelines('123')
 95 with open('user_pwd.txt','r') as read_file:
 96     print(read_file.read())
 97     #結果還是123     #readlines接收列表
 98 
 99 with open('user_pwd.txt','w') as file :
100     file.writelines(['stu1    123\n','stu2    123\n','stu3    123\n'])
101 with open('user_pwd.txt','r') as read_file:
102     print(read_file.readlines())
103     #需要手動指定換行符
104 '''
105 
106 '''
107 username = input('please enter your username:')
108 password = input('please enter your password:')
109 with open('user_pwd.txt','w') as file :
110     file.writelines([username,password])
111 with open('user_pwd.txt','r') as read_file:
112     print(read_file.readlines())
113 #這樣寫格式還是不對
114 '''
115 
116 '''
117 username_list = []
118 username = input('please enter your username:')
119 username_list.append(username)
120 #print(username_list)
121 password_list = []
122 password = input('please enter your password:')
123 password_list.append(password)
124 #print(password_list)
125 with open('user_pwd.txt','a') as file :
126     for i in range(max(len(username_list),len(password_list))):
127         try:                #try的思路可以學習一下，try/except
128             file.write("{}\t{}\n".format(username_list[i],password_list[i]))
129         except IndexError:
130             if len(username_list) > len(password_list):
131                 file.write('{}\t\n'.format(username_list[i]))
132             else:
133                 file.write('\t{}\n'.format((password_list[i])))
134 with open('user_pwd.txt','r') as read_file:
135     print(read_file.read())
136 '''
137 
138 
139 #open的模式
140 '''
141 mode is an optional string that specifies the mode in which the file
142     is opened. It defaults to 'r' which means open for reading in text
143     mode.  Other common values are 'w' for writing (truncating the file if
144     it already exists), 'x' for creating and writing to a new file, and
145     'a' for appending (which on some Unix systems, means that all writes
146     append to the end of the file regardless of the current seek position).
147     In text mode, if encoding is not specified the encoding used is platform
148     dependent: locale.getpreferredencoding(False) is called to get the
149     current locale encoding. (For reading and writing raw bytes use binary
150     mode and leave encoding unspecified.) The available modes are:
151 '''
152 
153 
154 '''
155     ========= ===============================================================
156     Character Meaning
157     --------- ---------------------------------------------------------------
158     'r'       open for reading (default)
159     'w'       open for writing, truncating the file first
160     'x'       create a new file and open it for writing
161     'a'       open for writing, appending to the end of the file if it exists
162     'b'       binary mode
163     't'       text mode (default)
164     '+'       open a disk file for updating (reading and writing)
165     'U'       universal newline mode (deprecated)
166     ========= ===============================================================
167     
168     The default mode is 'rt' (open for reading text). For binary random
169     access, the mode 'w+b' opens and truncates the file to 0 bytes, while
170     'r+b' opens the file without truncation. The 'x' mode implies 'w' and
171     raises an `FileExistsError` if the file already exists.
172 '''
173 
174 with open('song.txt','r',encoding='utf-8') as f:
175     #print(f.read())
176     #print('====>',f.read(23))
177     print(f.readline(3))
178     '''
179     for line in f:
180         #print(line)
181         print(line.rstrip())
182         #print(line,end='')
183     '''
184     #print(f.readlines())
185 print(f.closed)                 #檢視檔案是否被關閉