文件操作

#!/usr/bin/env python 
__author__ = "lrtao2010" 

#python3.7 文件操作


# r   只读,默认打开方式,当文件不存在时会报错
# w   只写,当文件不存在时会自动创建文件,文件内容只能是字符串,只能写入字符串
# r+  可读可写,当文件不存在时会报错
# w+  可读可写。当文件不存在时会新建
# a   追加文件,不可读
# a+  追加文件,可读可写
# rb  以二进制读模式打开,只可读
# rb+ 以二进制写读写模式打开,可读可写,当文件不存在时报错
# wb  以位进制写模式打开,只可写
# wb+ 以二进制读写模式打开,可读可写。当文件不存在时新建
# ab  以二进制追加模式打开,追加文件,不可读
# ab+ 以二进制读写模式打开,追加文件。可读可写

# with open("file.txt",'w',encoding='utf-8') as f:
#     print(f.readable())
#     print(f.writable())
#     False
#     True
# with open("file.txt",'r',encoding='utf-8') as f:
#     print(f.readable())
#     print(f.writable())
#     True
#     False
# with open("file.txt",'r+',encoding='utf-8') as f:
#     print(f.readable())
#     print(f.writable())
#     True
#     True
# with open("file.txt",'a',encoding='utf-8') as f:
#     print(f.readable())
#     print(f.writable())
#     False
#     True
# with open("file.txt",'a+',encoding='utf-8') as f:
#     print(f.readable())
#     print(f.writable())
#     True
#     True

# f= open("file1.txt",encoding='utf-8')#不写encoding,默认问操作系统编码
# file_data=f.read() #完全读取
# print(file_data)
# f.close() #需要执行关闭操作
# 1111
# 222
# 333
# 44
# 5555
# 666
# 你好!
# hello

# with open("file.txt",encoding='utf-8')as f:
#     file_data=f.read()
#     print(file_data)  #不需要执行close(),系统会自动关闭。
# 1111
# 222
# 333
# 44
# 5555
# 666
# 你好!
# hello

# with open("file.txt",encoding='utf-8')as f:
#     print(f.readable()) #判断是否可读
#     print(f.writable()) #判断是否可写
#     print(1, f.readline()) #一次只读一行
#     print(2, f.readline())
#     print(3, f.readline())
#     print(4, f.readline())
#     print(5, f.readline())
#     print(6, f.readline())
#     print(7, f.readline())
#     print(8, f.readline())
# True
# False
# 1 1111
#
# 2 222
#
# 3 333
#
# 4 44
#
# 5 5555
#
# 6 666
#
# 7 你好!
#
# 8 hello


#with open("file.txt",encoding='utf-8')as f:
#    print(f.readlines()) #将文件内容读取到列表中
#   ['1111\n', '222\n', '333\n', '44\n', '5555\n', '666\n', '你好!\n', 'hello']
#     for i in f.readlines():
#         print(i)
#         1111
#
#         222
#
#         333
#
#         44
#
#         5555
#
#         666
#
#         你好!
#
#         hello

# with open('file.txt','r',encoding='utf-8',newline='') as f:
# #     print(f.readlines())
# #     ['1111\r\n', '222\r\n', '333\r\n', '44\r\n', '5555\r\n', '666\r\n', '你好!\r\n', 'hello']
#     for i in f.readlines():
#         print(i,end='') #不打印换行符
#         1111
#         222
#         333
#         44
#         5555
#         666
#         你好!
#         hello

# with open('file.txt','w+',encoding='utf-8') as f: #原文件被清空后重新写入
#     f.write('a\n')
#     f.write('b\nc\n')
#     f.writelines(['d\n', 'e\n'])
#     f.seek(0) #将指针seek到0位置,否则读不出数据
#     print(f.read())
#     # a
#     # b
#     # c
#     # d
#     # e

# with open('file.txt','r+',encoding='utf-8') as f: #从指针位置所在处写入写入
#     print(f.readline())
#     f.write('a\n')
#     f.write('b\nc\n')
#     f.writelines(['d\n', 'e\n'])
#     f.seek(0) #将指针seek到0位置,否则读不出数据
#     print(f.read())
#     # 1111
#     #
#     # 1111
#     # 222
#     # 333
#     # 44
#     # 5555
#     # 666
#     # 你好!
#     # helloa
#     # b
#     # c
#     # d
#     # e

# with open('file.txt','a+',encoding='utf-8') as f:
#     f.write('写到文件最后')
#     f.seek(0)
#     print(f.read())
#     # 1111
#     # 222
#     # 333
#     # 44
#     # 5555
#     # 666
#     # 你好!
#     # hello写到文件最后

# with open('file.txt','a+',encoding='utf-8') as f:
#     print(f.encoding) #查看文件编码
#     #utf - 8

# #'字符串'---------encode---------》bytes
# #bytes---------decode---------》'字符串'

# with open('file.txt','rb') as f: #b模式不能指定编码
#     file_data=f.read()
#     print(file_data)
#     print(file_data.decode('utf-8'))
#     # b'1111\r\n222\r\n333\r\n44\r\n5555\r\n666\r\n\xe4\xbd\xa0\xe5\xa5\xbd!\r\nhello'
#     # 1111
#     # 222
#     # 333
#     # 44
#     # 5555
#     # 666
#     # 你好!
#     # hello

# with open('file.txt','wb+') as f:
#     file_data = 'test wb'
#     f.write(file_data.encode('utf-8'))
#     f.seek(0)
#     print(f.read())
#     # b'test wb'

# flush() 文件内容从内存刷到硬盘
# tell()  查看文件当前光标位置
# seek(3) #从开头开始算,将光标移动到第三个字节
          #seek 有三种工作方式,seek(offset[, whence])
          #seek(2,0)=seek(2),0是默认方式,相当于从0字节位置开始
          #seek(2,1)   1 相对当前位置
          #seek(-2,2)  2 从文件末尾开始
# truncate(10) #从开头开始算,将文件只保留从0-10个字节的内容,文件打开方式必须包含"写",
               #但是w和w+除外,因为这两种方式会首先把文件清空。
# with open('file.txt','ab') as f:
#     f.truncate(1)


#打印文件最后一行
# with open("file.txt",'rb') as f:
#     for i in f:   #这种方式不会读取整个文件,需要从哪里读取才从哪里开始读取,循环文件的推荐方式
#         offs=-5         #偏移量,根据一行大小确定
#         while True:
#             f.seek(offs,2)
#             data=f.readlines()
#             if len(data) > 1:
#                 print('这是最后一行:',data[-1].decode('utf-8'))
#                 break
#             offs*=2

# 这是最后一行: hello你好!hello你好!hello你好!hello你好!

澳门葡京备用网址,文件操作。 

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