一，open() 函数 处理文件
open函数，该函数用于文件处理
操作文件时，一般需要经历如下步骤：
- 打开文件
- 操作文件
一、打开文件
文件句柄 = open('文件路径', '模式')
打开文件时，需要指定文件路径和以何等方式打开文件，打开后，即可获取该文件句柄，日后通过此文件句柄对该文件操作。
1 文件句柄 = open('文件路径','打开模式')
文件句柄相当于于变量名，文件路径可以写为绝对路径也可以写为相对路径。
文件句柄可以循环 每次1行
for line in 文件句柄：
文件句柄.write("新文件")
打开文件的模式有：
- r ，只读模式【默认】
- w，只写模式【不可读；不存在则创建；存在则清空内容；】
- x， 只写模式【不可读；不存在则创建，存在则报错】
- a， 追加模式【不可读； 不存在则创建；存在则只追加内容；】
"+" 表示可以同时读写某个文件
- r+， 读写【可读，可写】
- w+，写读【可读，可写】
- x+ ，写读【可读，可写】
- a+， 写读【可读，可写】
"b"表示以字节的方式操作
- rb 或 r+b
- wb 或 w+b
- xb 或 w+b
- ab 或 a+b
注：以b方式打开时，读取到的内容是字节类型，写入时也需要提供字节类型
文件 hello.txt
Hello Word!
123
abc
456
abc
789
abc
刘建佐
代码 ：
f = open("hello.txt",'rb') # 用到b模式的时候 就不能跟 编码了。
data = f.read()
f.close()
print(data)
输出
C:Python35python3.exe E:/py_test/s5/open.py
b'Hello Word!
123
abc
456
abc
789
abc
xe5x88x98xe5xbbxbaxe4xbdx90'
python open函数 r 和rb区别
下面着重讲解下用"+" 同时读写某个文件的操作
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# r+形式 写的时候在末尾追加，指针移到到最后# 大家一定要清楚的明白读写的时候指针指向的位置，下面的这个例子一定要懂# f.tell() 读取指针的位置# f.seek(0) 设置指针的位置with open('1.txt','r+',encoding='utf-8') as f: print(f.tell()) #打印下 文件开始时候指针指向哪里 这里指向 0 print(f.read()) #读出文件内容'字符串'， print(f.tell()) #文件指针指到 9，一个汉子三个字符串，指针是以字符为单位 f.write('科比') #写入内容'科比',需要特别注意此时文件指到文件末尾去了 print(f.read()) #指针到末尾去了，所以读取的内容为空 print(f.tell()) #指针指到15 f.seek(0) #将指针内容指到 0 位置 print(f.read()) #因为文件指针指到开头去了，所以可以读到内容 字符串科比 # w+形式 存在的话先清空 一写的时候指针到最后with open('1.txt','w+') as f: f.write('Kg') #1.txt存在，所以将内面的内容清空，然后再写入 'kg' print(f.tell()) #此时指针指向2 print(f.read()) #读不到内容，因为指针指向末尾了 f.seek(0) print(f.read()) #读到内容，因为指针上一步已经恢复到起始位置 # a+打开的时候指针已经移到最后，写的时候不管怎样都往文件末尾追加，这里就不再演示了，读者可以自己试一下# x+文件存在的话则报错，也不演示了 |
Python文件读取方式
| 模式 | 说明 |
| read([size]) | 读取文件全部内容，如果设置了size，那么就读取size字节 |
| readline([size]) | 一行一行的读取 |
| readlines() | 读取到的每一行内容作为列表中的一个元素 |
二、操作
1 class file(object) 2 def close(self): # real signature unknown; restored from __doc__ 3 关闭文件 4 """ 5 close() -> None or (perhaps) an integer. Close the file. 6 7 Sets data attribute .closed to True. A closed file cannot be used for 8 further I/O operations. close() may be called more than once without 9 error. Some kinds of file objects (for example, opened by popen()) 10 may return an exit status upon closing. 11 """ 12 13 def fileno(self): # real signature unknown; restored from __doc__ 14 文件描述符 15 """ 16 fileno() -> integer "file descriptor". 17 18 This is needed for lower-level file interfaces, such os.read(). 19 """ 20 return 0 21 22 def flush(self): # real signature unknown; restored from __doc__ 23 刷新文件内部缓冲区 24 """ flush() -> None. Flush the internal I/O buffer. """ 25 pass 26 27 28 def isatty(self): # real signature unknown; restored from __doc__ 29 判断文件是否是同意tty设备 30 """ isatty() -> true or false. True if the file is connected to a tty device. """ 31 return False 32 33 34 def next(self): # real signature unknown; restored from __doc__ 35 获取下一行数据，不存在，则报错 36 """ x.next() -> the next value, or raise StopIteration """ 37 pass 38 39 def read(self, size=None): # real signature unknown; restored from __doc__ 40 读取指定字节数据 41 """ 42 read([size]) -> read at most size bytes, returned as a string. 43 44 If the size argument is negative or omitted, read until EOF is reached. 45 Notice that when in non-blocking mode, less data than what was requested 46 may be returned, even if no size parameter was given. 47 """ 48 pass 49 50 def readinto(self): # real signature unknown; restored from __doc__ 51 读取到缓冲区，不要用，将被遗弃 52 """ readinto() -> Undocumented. Don't use this; it may go away. """ 53 pass 54 55 def readline(self, size=None): # real signature unknown; restored from __doc__ 56 仅读取一行数据 57 """ 58 readline([size]) -> next line from the file, as a string. 59 60 Retain newline. A non-negative size argument limits the maximum 61 number of bytes to return (an incomplete line may be returned then). 62 Return an empty string at EOF. 63 """ 64 pass 65 66 def readlines(self, size=None): # real signature unknown; restored from __doc__ 67 读取所有数据，并根据换行保存值列表 68 """ 69 readlines([size]) -> list of strings, each a line from the file. 70 71 Call readline() repeatedly and return a list of the lines so read. 72 The optional size argument, if given, is an approximate bound on the 73 total number of bytes in the lines returned. 74 """ 75 return [] 76 77 def seek(self, offset, whence=None): # real signature unknown; restored from __doc__ 78 指定文件中指针位置 79 """ 80 seek(offset[, whence]) -> None. Move to new file position. 81 82 Argument offset is a byte count. Optional argument whence defaults to 83 (offset from start of file, offset should be >= 0); other values are 1 84 (move relative to current position, positive or negative), and 2 (move 85 relative to end of file, usually negative, although many platforms allow 86 seeking beyond the end of a file). If the file is opened in text mode, 87 only offsets returned by tell() are legal. Use of other offsets causes 88 undefined behavior. 89 Note that not all file objects are seekable. 90 """ 91 pass 92 93 def tell(self): # real signature unknown; restored from __doc__ 94 获取当前指针位置 95 """ tell() -> current file position, an integer (may be a long integer). """ 96 pass 97 98 def truncate(self, size=None): # real signature unknown; restored from __doc__ 99 截断数据，仅保留指定之前数据 100 """ 101 truncate([size]) -> None. Truncate the file to at most size bytes. 102 103 Size defaults to the current file position, as returned by tell(). 104 """ 105 pass 106 107 def write(self, p_str): # real signature unknown; restored from __doc__ 108 写内容 109 """ 110 write(str) -> None. Write string str to file. 111 112 Note that due to buffering, flush() or close() may be needed before 113 the file on disk reflects the data written. 114 """ 115 pass 116 117 def writelines(self, sequence_of_strings): # real signature unknown; restored from __doc__ 118 将一个字符串列表写入文件 119 """ 120 writelines(sequence_of_strings) -> None. Write the strings to the file. 121 122 Note that newlines are not added. The sequence can be any iterable object 123 producing strings. This is equivalent to calling write() for each string. 124 """ 125 pass 126 127 def xreadlines(self): # real signature unknown; restored from __doc__ 128 可用于逐行读取文件，非全部 129 """ 130 xreadlines() -> returns self. 131 132 For backward compatibility. File objects now include the performance 133 optimizations previously implemented in the xreadlines module. 134 """ 135 pass 136 137 2.x 138 139 2.x Code
class TextIOWrapper(_TextIOBase): """ Character and line based layer over a BufferedIOBase object, buffer. encoding gives the name of the encoding that the stream will be decoded or encoded with. It defaults to locale.getpreferredencoding(False). errors determines the strictness of encoding and decoding (see help(codecs.Codec) or the documentation for codecs.register) and defaults to "strict". newline controls how line endings are handled. It can be None, '', ' ', ' ', and ' '. It works as follows: * On input, if newline is None, universal newlines mode is enabled. Lines in the input can end in ' ', ' ', or ' ', and these are translated into ' ' before being returned to the caller. If it is '', universal newline mode is enabled, but line endings are returned to the caller untranslated. If it has any of the other legal values, input lines are only terminated by the given string, and the line ending is returned to the caller untranslated. * On output, if newline is None, any ' ' characters written are translated to the system default line separator, os.linesep. If newline is '' or ' ', no translation takes place. If newline is any of the other legal values, any ' ' characters written are translated to the given string. If line_buffering is True, a call to flush is implied when a call to write contains a newline character. """ def close(self, *args, **kwargs): # real signature unknown 关闭文件 pass def fileno(self, *args, **kwargs): # real signature unknown 文件描述符 pass def flush(self, *args, **kwargs): # real signature unknown 刷新文件内部缓冲区 pass def isatty(self, *args, **kwargs): # real signature unknown 判断文件是否是同意tty设备 pass def read(self, *args, **kwargs): # real signature unknown 读取指定字节数据 pass def readable(self, *args, **kwargs): # real signature unknown 是否可读 pass def readline(self, *args, **kwargs): # real signature unknown 仅读取一行数据 pass def seek(self, *args, **kwargs): # real signature unknown 指定文件中指针位置 pass def seekable(self, *args, **kwargs): # real signature unknown 指针是否可操作 pass def tell(self, *args, **kwargs): # real signature unknown 获取指针位置 pass def truncate(self, *args, **kwargs): # real signature unknown 截断数据，仅保留指定之前数据 pass def writable(self, *args, **kwargs): # real signature unknown 是否可写 pass def write(self, *args, **kwargs): # real signature unknown 写内容 pass def __getstate__(self, *args, **kwargs): # real signature unknown pass def __init__(self, *args, **kwargs): # real signature unknown pass @staticmethod # known case of __new__ def __new__(*args, **kwargs): # real signature unknown """ Create and return a new object. See help(type) for accurate signature. """ pass def __next__(self, *args, **kwargs): # real signature unknown """ Implement next(self). """ pass def __repr__(self, *args, **kwargs): # real signature unknown """ Return repr(self). """ pass buffer = property(lambda self: object(), lambda self, v: None, lambda self: None) # default closed = property(lambda self: object(), lambda self, v: None, lambda self: None) # default encoding = property(lambda self: object(), lambda self, v: None, lambda self: None) # default errors = property(lambda self: object(), lambda self, v: None, lambda self: None) # default line_buffering = property(lambda self: object(), lambda self, v: None, lambda self: None) # default name = property(lambda self: object(), lambda self, v: None, lambda self: None) # default newlines = property(lambda self: object(), lambda self, v: None, lambda self: None) # default _CHUNK_SIZE = property(lambda self: object(), lambda self, v: None, lambda self: None) # default _finalizing = property(lambda self: object(), lambda self, v: None, lambda self: None) # default 3.x 3.x
操作示例：
测试的文件名是 "hello.txt" ，文件内容为：
Hello Word! 123 abc 456 abc 789 abc
read 方法
代码：
# 以只读的方式打开文件hello.txt
f = open("hello.txt","r")
# 读取文件内容赋值给变量c
c = f.read()
# 关闭文件
f.close()
# 输出c的值
print(c)
输出结果
C:Python35python3.exe E:/py_test/s5/open.py
Hello Word!
123
abc
456
abc
789
abc
readline
代码：
# 以只读模式打开文件hello.txt
f = open("hello.txt","r")
# 读取第一行 strip 去除空行
c1 = f.readline().strip()
# 读取第二行
c2 = f.readline().strip()
# 读取第三行
c3 = f.readline().strip()
# 关闭文件
f.close()
# 输出读取文件第一行内容
print(c1)
# 输出读取文件第二行内容
print(c2)
# 输出读取文件第三行内容
print(c3)
C:Python35python.exe F:/Python_code/sublime/Day06/file.py
Hello Word!
123
abc
readlines 获取到的是列表，每行是列表的元素
用法
# 以只读的方式打开文件hello.txt
f = open("hello.txt","r")
# 将文件所有内容赋值给c
c = f.readlines()
# 查看数据类型
print(type(c))
# 关闭文件
f.close()
# 遍历输出文件内容 # n.strip()去除空行
for n in c:
print(n.strip())
Python文件写入方式
| 方法 | 说明 |
| write(str) | 将字符串写入文件 ，原文件内容存在则清空，不存在新建 |
| writelines(sequence or strings) | 写多行到文件，参数可以是一个可迭代的对象，列表、元组等 |
write
代码：
# 以只读的模式打开文件write.txt，没有则创建，有则覆盖内容
file = open("write.txt","w")
# 在文件内容中写入字符串test write
file.write("test write")
# 关闭文件
file.close()
writeline
代码：
# 以只读模式打开一个不存在的文件wr_lines.txt
f = open("wr_lines.txt","w",encoding="utf-8")
# 写入一个列表
f.writelines(["11","22","33"])
# 关闭文件
f.close()
wr_lines.txt 文件内容：
112233
Python文件操作所提供的方法
close(self):
关闭已经打开的文件
f.close()
fileno(self):
文件描述符
f = open("hello.txt",'rb')
data = f.fileno()
f.close()
print(data)
输出结果
C:Python35python3.exe E:/py_test/s5/open.py
3
flush(self):
刷新缓冲区的内容到硬盘中
f.flush() #在r+ 或者 rb+模式下还没有 f.close（） 或者之后，flush方法 就会将内存的数据写入硬盘。 否则在其他地方调用这个文件的新内容会找不到
isatty(self):
判断文件是否是tty设备，如果是tty设备则返回 True ，否则返回 False
f = open("hello.txt","r")
ret = f.isatty()
f.close()
print(ret)
返回结果：
C:Python35python.exe F:/Python_code/sublime/Day06/file.py False
readable(self):
是否可读，如果可读返回 True ，否则返回 False
f = open("hello.txt","r")
ret = f.readable()
f.close()
print(ret)
返回结果：
C:Python35python.exe F:/Python_code/sublime/Day06/file.py True
readline(self, limit=1):
每次仅读取一行数据
f = open("hello.txt","r")
print(f.readline())
print(f.readline())
f.close()
返回结果：
C:Python35python.exe F:/Python_code/sublime/Day06/file.py Hello Word! 123
readlines(self, hint=1):
把每一行内容当作列表中的一个元素
f = open("hello.txt","r")
print(f.readlines())
f.close()
返回结果：
C:Python35python.exe F:/Python_code/sublime/Day06/file.py ['Hello Word! ', '123 ', 'abc ', '456 ', 'abc ', '789 ', 'ab c']
tell(self):
获取指针位置
f = open("hello.txt","r")
print(f.tell())
f.close()
返回结果:
C:Python35python.exe F:/Python_code/sublime/Day06/file.py 0
seek(self, offset, whence=io.SEEK_SET):
指定文件中指针位置
f = open("hello.txt","r")
print(f.tell())
f.seek(3)
print(f.tell())
f.close()
执行结果
C:Python35python.exe F:/Python_code/sublime/Day06/file.py 0 3
seekable(self):
指针是否可操作
f = open("hello.txt","r")
print(f.seekable())
f.close()
执行结果
C:Python35python.exe F:/Python_code/sublime/Day06/file.py True
writable(self):
是否可写
f = open("hello.txt","r")
print(f.writable())
f.close()
执行结果
C:Python35python.exe F:/Python_code/sublime/Day06/file.py False
writelines(self, lines):
写入文件的字符串序列，序列可以是任何迭代的对象字符串生产，通常是一个 字符串列表 。
f = open("wr_lines.txt","w")
f.writelines(["11","22","33"])
f.close()
执行结果
112233
read(self, n=None):
读取指定字节数据，后面不加参数默认读取全部
f = open("wr_lines.txt","r")
print(f.read(3))
f.seek(0)
print(f.read())
f.close()
执行结果
C:Python35python.exe F:/Python_code/sublime/Day06/file.py 112 112233
write(self, s):
往文件里面写内容
f = open("wr_lines.txt","w")
f.write("abcabcabc")
f.close()
文件内容
abcabcabc