如果字符串在文本文件中，如何检查 Python 并打印该行? [英] How to check in Python if string is in a text file and print the line?

问题描述

我要做的是检查是否在文本文件中找到了这个字符串.如果是这样，我希望它打印出该行，否则打印出一条消息.

到目前为止我已经实现了这段代码:

 def check_string(string):w = raw_input("请输入英文单词:")如果 w 在 open('example.txt').read():对于 w.readlines():印刷线别的:print('找不到翻译！')

我已经尝试过实现，但出现语法错误.

它说:

<块引用>

该行的语法无效——对于 w.readlines():

知道如何使用这行代码吗?

解决方案

你应该尝试这样的事情:

导入重新def check_string():#如果您不使用它们，则无需将参数传递给函数w = raw_input("请输入英文单词:")#使用`with`上下文管理器打开文件，它会自动为你关闭文件with open("example.txt") as f:发现 = 错误for line in f: #iterate over the file at a time (memory高效)if re.search("\b{0}\b".format(w),line): #如果找到的字符串在当前行，则打印它印刷线发现 = 真如果没有找到:print('找不到翻译！')check_string() #现在调用函数

如果您要搜索确切的单词而不仅仅是子字符串，那么我建议在此处使用 regex.

示例:

<预><代码>>>>进口重新>>>strs = "foo bar spamm">>>strs中的垃圾邮件"真的>>>bool(re.search("\b{0}\b".format("spam"),strs))错误的

What I am trying to do is to check whether this string is found in the text file. If it does, I want it to printout that line, else printout a message.

I have implemented this code so far:

 def check_string(string):

     w = raw_input("Input the English word: ")
        if w in open('example.txt').read():
            for w.readlines():
                print line
        else:
            print('The translation cannot be found!')

I've tried implementing that but I got a syntax error.

It says:

invalid syntax at the line -- for w.readlines():

Any idea on how to go with this line of code?

解决方案

You should try something like this:

import re
def check_string():
    #no need to pass arguments to function if you're not using them
    w = raw_input("Input the English word: ")

    #open the file using `with` context manager, it'll automatically close the file for you
    with open("example.txt") as f:
        found = False
        for line in f:  #iterate over the file one line at a time(memory efficient)
            if re.search("\b{0}\b".format(w),line):    #if string found is in current line then print it
                print line
                found = True
        if not found:
            print('The translation cannot be found!')

check_string() #now call the function

If you are searching for exact words instead of just sub-string then I would suggest using regex here.

Example:

>>> import re
>>> strs = "foo bar spamm"
>>> "spam" in strs        
True
>>> bool(re.search("\b{0}\b".format("spam"),strs))
False

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