文件操作

讀寫操作都在內存中，只有在close后才會保存到文件

r = open('江雪.txt','r',encoding='utf-8')

r.fileno()#返回文件描述符。中文返回3

r.flush()#操作完即保存到文件中，

r.close()

r.read()#單位為字符，可指定數量，默認全部讀取

r.readline()#默認一行

r.readlines()#默認剩余所有內容，顯示為一個列表

r.seek()#將光標移動到指定位置

r.tell()#查看當前光標的位置

r.truncate()#截斷，

r.write()

r ，只讀模式【默認】

w，只寫模式【不可讀；不存在則創建；存在則清空內容；】

x， 只寫模式【不可讀；不存在則創建，存在則報錯】

a， 追加模式【可讀； 不存在則創建；存在則只追加內容；】

"+" 表示可以同時讀寫某個文件

r+， 讀寫【可讀，可寫】 w+，寫讀【可讀，可寫】 x+ ，寫讀【可讀，可寫】 a+， 寫讀【可讀，可寫】 "b"表示以字節的方式操作

rb 或 r+b wb 或 w+b xb 或 w+b ab 或 a+b

注：以b方式打開時，讀取到的內容是字節類型，寫入時也需要提供字節類型

r+:讀管自己讀，寫的話，從最后開始寫

w+：首先就是清空，write之后進行read，但是read是從write的光標位置開始讀

a+：光標開始就是最后，和r+的區別只是初始光標位置

無法直接修改原文件，只能通過創建新文件，進行修改和添加

with open('江雪.txt','r',encoding='utf-8') as r:#功能同上，只是退出with時，自動close

在Python 2.7 后，with又支持同時對多個文件的上下文進行管理，即：

withopen('log1') as obj1,open('log2') as obj2:

r = open('江雪.txt','r',encoding='utf-8')

# for i in r.readlines():錯誤姿勢，可以執行，但會一次性把所有的東西取到內存中

for i in r:#正確的姿勢：for內部將r這個文件對象做成一個迭代器，用一行去一行。

def read(self, size=-1): #known case of _io.FileIO.read

"""注意，不一定能全讀回來

Read at most size bytes, returned as bytes.

Only makes one system call, so less data may be returned than requested.

In non-blocking mode, returns None if no data is available.

Return an empty bytes object at EOF."""

return ""

def readline(self, *args, **kwargs):pass

def readlines(self, *args, **kwargs):pass

def tell(self, *args, **kwargs): #real signature unknown

"""Current file position.

Can raise OSError for non seekable files."""

pass

def seek(self, *args, **kwargs): #real signature unknown

"""Move to new file position and return the file position.

Argument offset is a byte count. Optional argument whence defaults to

SEEK_SET or 0 (offset from start of file, offset should be >= 0); other values

are SEEK_CUR or 1 (move relative to current position, positive or negative),

and SEEK_END or 2 (move relative to end of file, usually negative, although

many platforms allow seeking beyond the end of a file).

Note that not all file objects are seekable."""

pass

def write(self, *args, **kwargs): #real signature unknown

"""Write bytes b to file, return number written.

Only makes one system call, so not all of the data may be written.

The number of bytes actually written is returned. In non-blocking mode,

returns None if the write would block."""

pass

def flush(self, *args, **kwargs):pass

def truncate(self, *args, **kwargs): #real signature unknown

"""Truncate the file to at most size bytes and return the truncated size.

Size defaults to the current file position, as returned by tell().

The current file position is changed to the value of size."""

pass

def close(self): #real signature unknown; restored from __doc__

"""Close the file.

A closed file cannot be used for further I/O operations. close() may be

called more than once without error."""

pass

##############################################################less usefull

def fileno(self, *args, **kwargs): #real signature unknown

"""Return the underlying file descriptor (an integer)."""

pass

def isatty(self, *args, **kwargs): #real signature unknown

"""True if the file is connected to a TTY device."""

pass

def readable(self, *args, **kwargs): #real signature unknown

"""True if file was opened in a read mode."""

pass

def readall(self, *args, **kwargs): #real signature unknown

"""Read all data from the file, returned as bytes.

In non-blocking mode, returns as much as is immediately available,

or None if no data is available. Return an empty bytes object at EOF."""

pass

def seekable(self, *args, **kwargs): #real signature unknown

"""True if file supports random-access."""

pass

def writable(self, *args, **kwargs): #real signature unknown

"""True if file was opened in a write mode."""

pass操作方法介紹

操作方法介紹

classTextIOWrapper(_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, '',

'\n', '\r', and '\r\n'. It works as follows:

* On input, if newline is None, universal newlines mode is

enabled. Lines in the input can end in '\n', '\r', or '\r\n', and

these are translated into '\n' 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 '\n' characters written are

translated to the system default line separator, os.linesep. If

newline is '' or '\n', no translation takes place. If newline is any

of the other legal values, any '\n' 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

關閉文件pass

def fileno(self, *args, **kwargs): #real signature unknown

文件描述符pass

def flush(self, *args, **kwargs): #real signature unknown

刷新文件內部緩沖區pass

def isatty(self, *args, **kwargs): #real signature unknown

判斷文件是否是同意tty設備pass

def read(self, *args, **kwargs): #real signature unknown

讀取指定字節數據pass

def readable(self, *args, **kwargs): #real signature unknown

是否可讀pass

def readline(self, *args, **kwargs): #real signature unknown

僅讀取一行數據pass

def seek(self, *args, **kwargs): #real signature unknown

指定文件中指針位置pass

def seekable(self, *args, **kwargs): #real signature unknown

指針是否可操作pass

def tell(self, *args, **kwargs): #real signature unknown

獲取指針位置pass

def truncate(self, *args, **kwargs): #real signature unknown

截斷數據，僅保留指定之前數據pass

def writable(self, *args, **kwargs): #real signature unknown

是否可寫pass

def write(self, *args, **kwargs): #real signature unknown

寫內容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)."""

passbuffer= 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

文件操作3.x

classfile(object)def close(self): #real signature unknown; restored from __doc__

關閉文件"""close() -> None or (perhaps) an integer. Close the file.

Sets data attribute .closed to True. A closed file cannot be used for

further I/O operations. close() may be called more than once without

error. Some kinds of file objects (for example, opened by popen())

may return an exit status upon closing."""

def fileno(self): #real signature unknown; restored from __doc__

文件描述符"""fileno() -> integer "file descriptor".

This is needed for lower-level file interfaces, such os.read()."""

return0def flush(self): #real signature unknown; restored from __doc__

刷新文件內部緩沖區"""flush() -> None. Flush the internal I/O buffer."""

pass

def isatty(self): #real signature unknown; restored from __doc__

判斷文件是否是同意tty設備"""isatty() -> true or false. True if the file is connected to a tty device."""

returnFalsedef next(self): #real signature unknown; restored from __doc__

獲取下一行數據，不存在，則報錯"""x.next() -> the next value, or raise StopIteration"""

pass

def read(self, size=None): #real signature unknown; restored from __doc__

讀取指定字節數據"""read([size]) -> read at most size bytes, returned as a string.

If the size argument is negative or omitted, read until EOF is reached.

Notice that when in non-blocking mode, less data than what was requested

may be returned, even if no size parameter was given."""

pass

def readinto(self): #real signature unknown; restored from __doc__

讀取到緩沖區，不要用，將被遺棄"""readinto() -> Undocumented. Don't use this; it may go away."""

pass

def readline(self, size=None): #real signature unknown; restored from __doc__

僅讀取一行數據"""readline([size]) -> next line from the file, as a string.

Retain newline. A non-negative size argument limits the maximum

number of bytes to return (an incomplete line may be returned then).

Return an empty string at EOF."""

pass

def readlines(self, size=None): #real signature unknown; restored from __doc__

讀取所有數據，并根據換行保存值列表"""readlines([size]) -> list of strings, each a line from the file.

Call readline() repeatedly and return a list of the lines so read.

The optional size argument, if given, is an approximate bound on the

total number of bytes in the lines returned."""

return[]def seek(self, offset, whence=None): #real signature unknown; restored from __doc__

指定文件中指針位置"""seek(offset[, whence]) -> None. Move to new file position.

Argument offset is a byte count. Optional argument whence defaults to

(offset from start of file, offset should be >= 0); other values are 1

(move relative to current position, positive or negative), and 2 (move

relative to end of file, usually negative, although many platforms allow

seeking beyond the end of a file). If the file is opened in text mode,

only offsets returned by tell() are legal. Use of other offsets causes

undefined behavior.

Note that not all file objects are seekable."""

pass

def tell(self): #real signature unknown; restored from __doc__

獲取當前指針位置"""tell() -> current file position, an integer (may be a long integer)."""

pass

def truncate(self, size=None): #real signature unknown; restored from __doc__

截斷數據，僅保留指定之前數據"""truncate([size]) -> None. Truncate the file to at most size bytes.

Size defaults to the current file position, as returned by tell()."""

pass

def write(self, p_str): #real signature unknown; restored from __doc__

寫內容"""write(str) -> None. Write string str to file.

Note that due to buffering, flush() or close() may be needed before

the file on disk reflects the data written."""

pass

def writelines(self, sequence_of_strings): #real signature unknown; restored from __doc__

將一個字符串列表寫入文件"""writelines(sequence_of_strings) -> None. Write the strings to the file.

Note that newlines are not added. The sequence can be any iterable object

producing strings. This is equivalent to calling write() for each string."""

pass

def xreadlines(self): #real signature unknown; restored from __doc__

可用于逐行讀取文件，非全部"""xreadlines() -> returns self.

For backward compatibility. File objects now include the performance

optimizations previously implemented in the xreadlines module."""

pass

2.x

文件操作2.x

使用Python內置的open()函數,打開一個文件對象,在磁盤中讀寫str、bytes

StringIO顧名思義就是在內存中讀寫str

BytesIO實現了在內存中讀寫bytes

我們把變量從內存中變成可存儲或傳輸的過程稱之為序列化

序列化之后，就可以把序列化后的內容寫入磁盤，或者通過網絡傳輸到別的機器上。

參考：https://www.cnblogs.com/yuanchenqi/articles/5782764.html

循環

if 條件1：

自拍

elif 條件2：

蹦

else：

跳舞

continue 結束本次循環，繼續下一次循環

break 跳出整個當前的循環(只能跳出一層)

If elif else 只執行其中一個

但while else；for else執行循環后，才執行else

for循環

while循環

總結

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