宠物网站页面设计模板,建设工程项目管理,frontpage导入网站,wordpress后台修改icp连接文件操作基本流程。 计算机系统分为#xff1a;计算机硬件#xff0c;操作系统#xff0c;应用程序三部分。 我们用python或其他语言编写的应用程序若想要把数据永久保存下来#xff0c;必须要保存于硬盘中#xff0c;这就涉及到应用程序要操作硬件#xff0c;众所周知计算机硬件操作系统应用程序三部分。 我们用python或其他语言编写的应用程序若想要把数据永久保存下来必须要保存于硬盘中这就涉及到应用程序要操作硬件众所周知应用程序是无法直接操作硬件的这就用到了操作系统。操作系统把复杂的硬件操作封装成简单的接口给用户/应用程序使用其中文件就是操作系统提供给应用程序来操作硬盘虚拟概念用户或应用程序通过操作文件可以将自己的数据永久保存下来。 有了文件的概念我们无需再去考虑操作硬盘的细节只需要关注操作文件的流程 #1. 打开文件得到文件句柄并赋值给一个变量
fopen(a.txt,r,encodingutf-8) #默认打开模式就为r#2. 通过句柄对文件进行操作
dataf.read()#3. 关闭文件
f.close() 关闭文件的注意事项 打开一个文件包含两部分资源操作系统级打开的文件应用程序的变量。在操作完毕一个文件时必须把与该文件的这两部分资源一个不落地回收回收方法为
1、f.close() #回收操作系统级打开的文件
2、del f #回收应用程序级的变量其中del f一定要发生在f.close()之后否则就会导致操作系统打开的文件还没有关闭白白占用资源
而python自动的垃圾回收机制决定了我们无需考虑del f这就要求我们在操作完毕文件后一定要记住f.close()虽然我这么说但是很多同学还是会很不要脸地忘记f.close(),对于这些不长脑子的同学我们推荐傻瓜式操作方式使用with关键字来帮我们管理上下文
with open(a.txt,w) as f:passwith open(a.txt,r) as read_f,open(b.txt,w) as write_f:dataread_f.read()write_f.write(data)注意 View Code 文件编码 fopen(...)是由操作系统打开文件那么如果我们没有为open指定编码那么打开文件的默认编码很明显是操作系统说了算了操作系统会用自己的默认编码去打开文件在windows下是gbk在linux下是utf-8。 #这就用到了上节课讲的字符编码的知识若要保证不乱码文件以什么方式存的就要以什么方式打开。
fopen(a.txt,r,encodingutf-8) 文件的打开模式 文件句柄 open‘文件路径’‘模式’ #1. 打开文件的模式有(默认为文本模式)
r 只读模式【默认模式文件必须存在不存在则抛出异常】
w只写模式【不可读不存在则创建存在则清空内容】
a 只追加写模式【不可读不存在则创建存在则只追加内容】#2. 对于非文本文件我们只能使用b模式b表示以字节的方式操作而所有文件也都是以字节的形式存储的使用这种模式无需考虑文本文件的字符编码、图片文件的jgp格式、视频文件的avi格式
rb
wb
ab
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不能指定编码#3,‘’模式就是增加了一个功能
r 读写【可读可写】
w写读【可写可读】
a 写读【可写可读】#4以bytes类型操作的读写写读写读模式
rb 读写【可读可写】
wb写读【可写可读】
ab 写读【可写可读】 文件操作方法。 常用操作方法。 read3 1. 文件打开方式为文本模式时代表读取3个字符 2. 文件打开方式为b模式时代表读取3个字节 其余的文件内光标移动都是以字节为单位的如seektelltruncate 注意 1. seek有三种移动方式012其中1和2必须在b模式下进行但无论哪种模式都是以bytes为单位移动的 2. truncate是截断文件所以文件的打开方式必须可写但是不能用w或w等方式打开因为那样直接清空文件了所以truncate要在r或a或a等模式下测试效果。 所有操作方法。 class file(object)def close(self): # real signature unknown; restored from __doc__关闭文件close() - None or (perhaps) an integer. Close the file.Sets data attribute .closed to True. A closed file cannot be used forfurther I/O operations. close() may be called more than once withouterror. 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().return 0def flush(self): # real signature unknown; restored from __doc__刷新文件内部缓冲区 flush() - None. Flush the internal I/O buffer. passdef isatty(self): # real signature unknown; restored from __doc__判断文件是否是同意tty设备 isatty() - true or false. True if the file is connected to a tty device. return Falsedef next(self): # real signature unknown; restored from __doc__获取下一行数据不存在则报错 x.next() - the next value, or raise StopIteration passdef read(self, sizeNone): # real signature unknown; restored from __doc__读取指定字节数据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 requestedmay be returned, even if no size parameter was given.passdef readinto(self): # real signature unknown; restored from __doc__读取到缓冲区不要用将被遗弃 readinto() - Undocumented. Dont use this; it may go away. passdef readline(self, sizeNone): # real signature unknown; restored from __doc__仅读取一行数据readline([size]) - next line from the file, as a string.Retain newline. A non-negative size argument limits the maximumnumber of bytes to return (an incomplete line may be returned then).Return an empty string at EOF.passdef readlines(self, sizeNone): # real signature unknown; restored from __doc__读取所有数据并根据换行保存值列表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 thetotal number of bytes in the lines returned.return []def seek(self, offset, whenceNone): # real signature unknown; restored from __doc__指定文件中指针位置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 (moverelative to end of file, usually negative, although many platforms allowseeking 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 causesundefined behavior.Note that not all file objects are seekable.passdef tell(self): # real signature unknown; restored from __doc__获取当前指针位置 tell() - current file position, an integer (may be a long integer). passdef truncate(self, sizeNone): # real signature unknown; restored from __doc__截断数据仅保留指定之前数据truncate([size]) - None. Truncate the file to at most size bytes.Size defaults to the current file position, as returned by tell().passdef write(self, p_str): # real signature unknown; restored from __doc__写内容write(str) - None. Write string str to file.Note that due to buffering, flush() or close() may be needed beforethe file on disk reflects the data written.passdef writelines(self, sequence_of_strings): # real signature unknown; restored from __doc__将一个字符串列表写入文件writelines(sequence_of_strings) - None. Write the strings to the file.Note that newlines are not added. The sequence can be any iterable objectproducing strings. This is equivalent to calling write() for each string.passdef xreadlines(self): # real signature unknown; restored from __doc__可用于逐行读取文件非全部xreadlines() - returns self.For backward compatibility. File objects now include the performanceoptimizations previously implemented in the xreadlines module.pass2.x 2.x class TextIOWrapper(_TextIOBase):Character and line based layer over a BufferedIOBase object, buffer.encoding gives the name of the encoding that the stream will bedecoded or encoded with. It defaults to locale.getpreferredencoding(False).errors determines the strictness of encoding and decoding (seehelp(codecs.Codec) or the documentation for codecs.register) anddefaults 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 isenabled. Lines in the input can end in \n, \r, or \r\n, andthese are translated into \n before being returned to thecaller. If it is , universal newline mode is enabled, but lineendings are returned to the caller untranslated. If it has any ofthe other legal values, input lines are only terminated by the givenstring, and the line ending is returned to the caller untranslated.* On output, if newline is None, any \n characters written aretranslated to the system default line separator, os.linesep. Ifnewline is or \n, no translation takes place. If newline is anyof the other legal values, any \n characters written are translatedto the given string.If line_buffering is True, a call to flush is implied when a call towrite contains a newline character.def close(self, *args, **kwargs): # real signature unknown关闭文件passdef fileno(self, *args, **kwargs): # real signature unknown文件描述符passdef flush(self, *args, **kwargs): # real signature unknown刷新文件内部缓冲区passdef isatty(self, *args, **kwargs): # real signature unknown判断文件是否是同意tty设备passdef read(self, *args, **kwargs): # real signature unknown读取指定字节数据passdef readable(self, *args, **kwargs): # real signature unknown是否可读passdef readline(self, *args, **kwargs): # real signature unknown仅读取一行数据passdef seek(self, *args, **kwargs): # real signature unknown指定文件中指针位置passdef seekable(self, *args, **kwargs): # real signature unknown指针是否可操作passdef tell(self, *args, **kwargs): # real signature unknown获取指针位置passdef truncate(self, *args, **kwargs): # real signature unknown截断数据仅保留指定之前数据passdef writable(self, *args, **kwargs): # real signature unknown是否可写passdef write(self, *args, **kwargs): # real signature unknown写内容passdef __getstate__(self, *args, **kwargs): # real signature unknownpassdef __init__(self, *args, **kwargs): # real signature unknownpassstaticmethod # known case of __new__def __new__(*args, **kwargs): # real signature unknown Create and return a new object. See help(type) for accurate signature. passdef __next__(self, *args, **kwargs): # real signature unknown Implement next(self). passdef __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) # default3.x 3.x 文件的修改。 文件的数据是存放于硬盘上的因而只存在覆盖、不存在修改这么一说我们平时看到的修改文件都是模拟出来的效果具体的说有两种实现方式 方式一将硬盘存放的该文件的内容全部加载到内存在内存中是可以修改的修改完毕后再由内存覆盖到硬盘wordvimnodpad等编辑器 import os # 调用系统模块with open(a.txt) as read_f,open(.a.txt.swap,w) as write_f:dataread_f.read() #全部读入内存,如果文件很大,会很卡datadata.replace(alex,SB) #在内存中完成修改
write_f.write(data) #一次性写入新文件os.remove(a.txt) #删除原文件
os.rename(.a.txt.swap,a.txt) #将新建的文件重命名为原文件 方法一 方式二将硬盘存放的该文件的内容一行一行地读入内存修改完毕就写入新文件最后用新文件覆盖源文件 import oswith open(a.txt) as read_f,open(.a.txt.swap,w) as write_f:for line in read_f:lineline.replace(alex,SB)write_f.write(line)os.remove(a.txt)
os.rename(.a.txt.swap,a.txt) 方法二 转载于:https://www.cnblogs.com/wy3713/p/9135639.html
