python循环读一个文件

python 循环读一个文件

Python按行读文件1. 最基本的读文件方法：# File: readline-example-1.pyfile = open("sample.txt")while 1:line = file.readline()if not line:breakpass # do something一行一行得从文件读数据，显然比较慢；不过很省内存。

python 多个文件怎么调用

同时打开三个文件，文件行数一样，要求实现每个文件依次读取一行，然后输出，我们先来看比较容易想到的写法：with open(filename1, 'rb') as fp1:with open(filename2, 'rb') as fp2:with open(filename3, 'rb') as fp3:for i in fp1:j = fp2.readline()k = fp3.readline()print(i, j, k)注意这里只能对单个文件进行for循环读取，不能写成：for i, j, k in fp1, fp2, fp3:print(i, j, k)但可使用强大的zip操作：for i, j, k in zip(fp1, fp2, fp3):print(i, j, k)这样层层的嵌套未免啰嗦，with结构支持一种更简洁的写法：with open(filename1, 'rb') as fp1, open(filename2, 'rb') as fp2, open(filename3, 'rb') as fp3:for i in fp1:j = fp2.readline()k = fp3.readline()print(i, j, k)或者使用更为优雅的写法，此时需要contextlib语法糖：from contextlib improt ExitStackwith ExitStack() as stack:files = [stack.enter_context(open(fname)) for fname in [filename1, filename2, filename3]]for i, j, k in zip(files[0], files[1], files[2]):print(i, j, k)

Python循环读文件

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