非常简单的嵌套文件迭代的行为不符合预期

Question

我正在编写一个python脚本来解析2个文本文件，查找某行中第二个文本的内容是否与第一个相同，如果是这样，请使用另一个变量替换它

尝试对文件执行for循环时会出现问题，例如以下代码：

ase = open('text1.txt','r')
endurance = open('text2.txt','r')

for x in ase:
 print('sheet')
 for y in endurance:
    print('yayyeeeeet')

举个例子，text1有100行，text2也有， 输出应为：

sheet
yayyeeeeet
yayyeeeeet
yayyeeeeet
yayyeeeeet x100

然后再次以sheet和100xyayyeeeet开始100个循环， 但输出不同，如下所示：

sheet
yayyeeeeet
yayyeeeeet
yayyeeeeet
yayyeeeeet
yayyeeeeet
yayyeeeeet
yayyeeeeet
yayyeeeeet
yayyeeeeet
yayyeeeeet
yayyeeeeet
yayyeeeeet
yayyeeeeet
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yayyeeeeet
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我就是不明白为什么会这样 使用Python2.7和Python3.8进行测试

Answer 1

正如保罗·汉金所说：耐力是一个迭代器。你只能用一次。 请尝试以下方法：

with open('text2.txt','r') as f:
    endurance = f.readlines()

Answer 2

您可以在打开的文件上迭代一次。。。因此，我建议使用readlines()来代替：

ase = open('test.txt','r').readlines()    #< - add .readlines() here
endurance = open('text2.txt','r').readlines()  #< - add .readlines()

for x in ase:
    print('sheet')
    for y in endurance:
        print('yayyeeeeet')

此外，关闭任何打开的文件也是一种很好的做法。所以，我真的建议使用with语句

Answer 3

迭代器在使用完之后不会自动重置。最简单的解决方案是每次重新打开“内部”文件

with open('text1.txt','r') as ase:
    for x in ase:
        print('sheet')
        with open('text2.txt','r') as endurance:
            for y in endurance:
                print('yayyeeeeet')

这避免了将整个文件读入内存的需要

---

如果希望两个文件都保持打开状态，可以使用seek方法将第二个文件放在开头，但我认为这不能保证与迭代器结合使用。不过，您可以使用对readline的显式调用

with open('text1.txt') as ase, open('text2.txt') as endurance:
    for x in ase:
        print('sheet')
        endurance.seek(0)
        for y in iter(endurance.readline, ''):
            print('yayyeeeeet')