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基本步骤
常用函数
open()函数
close()函数
read()函数
readlines()函数
readline()函数
write()函数
writelines()函数
with语句
读写操作的应用#xff1a;
拷贝文件 with 语句的嵌套
逐行拷贝 基本步骤
1. 打开文件#xff1a;open(filepath, mode, en…目录
基本步骤
常用函数
open()函数
close()函数
read()函数
readlines()函数
readline()函数
write()函数
writelines()函数
with语句
读写操作的应用
拷贝文件 with 语句的嵌套
逐行拷贝 基本步骤
1. 打开文件open(filepath, mode, encoding)
2. 读写文件read() / write()
3. 关闭文件close()
python读取文件操作实例 f open(filename.txt, r, encodingutf-8) f.read() f.close()
常用函数
open()函数
open(file, moder, buffering-1, encodingNone, errorsNone, newlineNone, closefdTrue, openerNone)
file是要打开的文件moder是打开文件的模式encoding是编码格式
文件的打开模式有以下字符表示 r open for reading (default) w open for writing, truncating the file first x create a new file and open it for writing a open for writing, appending to the end of the file if it exists b binary mode t text mode (default) open a disk file for updating (reading and writing)
打开模式还能连用
The default mode is rt (open for reading text). For binary random access, the mode wb opens and truncates the file to 0 bytes, while rb opens the file without truncation. The x mode implies w and raises an FileExistsError if the file already exists.
close()函数
close() method of _io.TextIOWrapper instance Flush and close the IO object. This method has no effect if the file is already closed
打开文件必须有对应的关闭否则该未关闭的文件不能被其它的应用操作。
read()函数
read(size-1, /) method of _io.TextIOWrapper instance Read at most size characters from stream. Read from underlying buffer until we have size characters or we hit EOF. If size is negative or omitted, read until EOF.
read()可选参数size可以用于读取“size”大小的数据返回的是字符串或字节对象若是size的值没有填写或者是个负值那么read()函数将读取文件的所有内容这也是用python开发pc软件中“复制黏贴”的功能比较常用的函数。
readlines()函数
Help on built-in function readlines:
readlines(hint-1, /) method of _io.TextIOWrapper instance Return a list of lines from the stream. hint can be specified to control the number of lines read: no more lines will be read if the total size (in bytes/characters) of all lines so far exceeds hint.
readlines()函数是将文件当中的所有行一行一行地读取并逐一写入一个列表list内最终返回这个列表。
readline()函数
Help on built-in function readline:
readline(size-1, /) method of _io.TextIOWrapper instance Read until newline or EOF. Return an empty string if EOF is hit immediately. If size is specified, at most size characters will be read.
readline()函数就是读取一行数据用法除了size参数之外就跟read()差不多也是open()打开文件readline()读取数据close()关闭文件
write()函数
write(text, /) method of _io.TextIOWrapper instance Write string s to stream. Return the number of characters written (which is always equal to the length of the string).
writelines()函数
writelines(lines, /) method of _io.TextIOWrapper instance Write a list of lines to stream. Line separators are not added, so it is usual for each of the lines provided to have a line separator at the end.
with语句
通过with语句不管读取还是写入文件操作都不用写对应的close()函数语句块结束系统会自动关闭文件。
with open(filename.txt, r, encodingurf-8) as f:f.read()
读写操作的应用
拷贝文件
# 打开源文件以读取内容
with open(source.txt, r) as source_file: source_content source_file.read() # 打开目标文件以写入内容
with open(destination.txt, w) as destination_file: destination_file.write(source_content) with 语句的嵌套
以上两个with语句块还能嵌套写在一起
# 打开源文件以读取内容并同时打开目标文件以写入内容
with open(source.txt, r) as source_file: with open(destination.txt, w) as destination_file: # 读取源文件的内容 source_content source_file.read() # 将读取的内容写入到目标文件中 destination_file.write(source_content)
可以写在同一行
# 打开源文件以读取内容并同时打开目标文件以写入内容
with open(source.txt, r) as source_file, open(destination.txt, w) as destination_file: # 读取源文件的内容 source_content source_file.read() # 将读取的内容写入到目标文件中 destination_file.write(source_content)
逐行拷贝
如果源文件很大使用read()方法一次性读取所有内容可能会消耗较多的内存。对于大文件更推荐的做法是使用文件对象的迭代器逐行读取和写入这样可以减少内存的使用。
with open(source.txt, r) as source_file, open(destination.txt, w) as destination_file: # 逐行读取源文件并写入目标文件 for line in source_file: destination_file.write(line) 完
