如何在文本文件中搜索字符串?-Python 实用宝典

如何在文本文件中搜索字符串?

我想检查字符串是否在文本文件中。如果是,请执行X。如果不是,请执行Y。但是,True由于某些原因,此代码始终返回。谁能看到哪里出了问题? def check(): datafile = file('example.txt') found = False for line in datafile: if blabla in line: found = True break check() if True: print "true" else: print "false"

问题:如何在文本文件中搜索字符串?

我想检查字符串是否在文本文件中。如果是,请执行X。如果不是,请执行Y。但是,True由于某些原因,此代码始终返回。谁能看到哪里出了问题?

def check():
    datafile = file('example.txt')
    found = False
    for line in datafile:
        if blabla in line:
            found = True
            break

check()
if True:
    print "true"
else:
    print "false"

I want to check if a string is in a text file. If it is, do X. If it's not, do Y. However, this code always returns True for some reason. Can anyone see what is wrong?

def check():
    datafile = file('example.txt')
    found = False
    for line in datafile:
        if blabla in line:
            found = True
            break

check()
if True:
    print "true"
else:
    print "false"

回答 0

您一直得到的原因True已经给出,因此我只提供另一个建议:

如果文件不是太大,则可以将其读取为字符串,然后使用它(比读取和检查每行更容易,并且通常更快):

with open('example.txt') as f:
    if 'blabla' in f.read():
        print("true")

另一个技巧:通过使用mmap.mmap()创建使用基础文件的“字符串状”对象(而不是读取内存中的整个文件),可以减轻可能的内存问题:

import mmap

with open('example.txt') as f:
    s = mmap.mmap(f.fileno(), 0, access=mmap.ACCESS_READ)
    if s.find('blabla') != -1:
        print('true')

注意:在python 3中,mmap的行为类似于bytearray对象而不是字符串,因此,例如,查找的子序列也find()必须是bytes对象而不是字符串。s.find(b'blabla')

#!/usr/bin/env python3
import mmap

with open('example.txt', 'rb', 0) as file, \
     mmap.mmap(file.fileno(), 0, access=mmap.ACCESS_READ) as s:
    if s.find(b'blabla') != -1:
        print('true')

您还可以在mmap不区分大小写的搜索中使用正则表达式:if re.search(br'(?i)blabla', s):

The reason why you always got True has already been given, so I'll just offer another suggestion:

If your file is not too large, you can read it into a string, and just use that (easier and often faster than reading and checking line per line):

with open('example.txt') as f:
    if 'blabla' in f.read():
        print("true")

Another trick: you can alleviate the possible memory problems by using mmap.mmap() to create a "string-like" object that uses the underlying file (instead of reading the whole file in memory):

import mmap

with open('example.txt') as f:
    s = mmap.mmap(f.fileno(), 0, access=mmap.ACCESS_READ)
    if s.find('blabla') != -1:
        print('true')

NOTE: in python 3, mmaps behave like bytearray objects rather than strings, so the subsequence you look for with find() has to be a bytes object rather than a string as well, eg. s.find(b'blabla'):

#!/usr/bin/env python3
import mmap

with open('example.txt', 'rb', 0) as file, \
     mmap.mmap(file.fileno(), 0, access=mmap.ACCESS_READ) as s:
    if s.find(b'blabla') != -1:
        print('true')

You could also use regular expressions on mmap e.g., case-insensitive search: if re.search(br'(?i)blabla', s):


回答 1

如Jeffrey Said所述,您没有检查的值check()。此外,您的check()函数未返回任何内容。注意区别:

def check():
    with open('example.txt') as f:
        datafile = f.readlines()
    found = False  # This isn't really necessary
    for line in datafile:
        if blabla in line:
            # found = True # Not necessary
            return True
    return False  # Because you finished the search without finding

然后,您可以测试的输出check()

if check():
    print('True')
else:
    print('False')

As Jeffrey Said, you are not checking the value of check(). In addition, your check() function is not returning anything. Note the difference:

def check():
    with open('example.txt') as f:
        datafile = f.readlines()
    found = False  # This isn't really necessary
    for line in datafile:
        if blabla in line:
            # found = True # Not necessary
            return True
    return False  # Because you finished the search without finding

Then you can test the output of check():

if check():
    print('True')
else:
    print('False')

回答 2

这是使用find函数可能回答您问题的另一种方法,该函数为您提供了真正存在位置的字面数值

open('file', 'r').read().find('')

在查找中输入您要查找的单词并'file'代表您的文件名

Here's another way to possibly answer your question using the find function which gives you a literal numerical value of where something truly is

open('file', 'r').read().find('')

in find write the word you want to find and 'file' stands for your file name


回答 3

if True:
    print "true"

这总是发生,因为True始终为True。

您想要这样的东西:

if check():
    print "true"
else:
    print "false"

祝好运!

if True:
    print "true"

This always happens because True is always True.

You want something like this:

if check():
    print "true"
else:
    print "false"

Good luck!


回答 4

为此,我做了一些功能。它在输入文件中搜索单词,然后将其添加到输出文件中。

def searcher(outf, inf, string):
    with open(outf, 'a') as f1:
        if string in open(inf).read():
            f1.write(string)
  • outf是输出文件
  • inf是输入文件
  • 字符串当然是您希望找到并添加到outf的所需字符串。

I made a little function for this purpose. It searches for a word in the input file and then adds it to the output file.

def searcher(outf, inf, string):
    with open(outf, 'a') as f1:
        if string in open(inf).read():
            f1.write(string)
  • outf is the output file
  • inf is the input file
  • string is of course, the desired string that you wish to find and add to outf.

回答 5

您的check函数应返回found布尔值,并使用该值确定要打印的内容。

def check():
        datafile = file('example.txt')
        found = False
        for line in datafile:
            if blabla in line:
                found = True
                break

        return found

found = check()
if found:
    print "true"
else:
    print "false"

第二块也可以浓缩为:

if check():
    print "true"
else:
    print "false"

Your check function should return the found boolean and use that to determine what to print.

def check():
        datafile = file('example.txt')
        found = False
        for line in datafile:
            if blabla in line:
                found = True
                break

        return found

found = check()
if found:
    print "true"
else:
    print "false"

the second block could also be condensed to:

if check():
    print "true"
else:
    print "false"

回答 6

两个问题:

  1. 您的函数不返回任何内容。没有明确返回任何内容的函数将返回None(这是错误的)

  2. True始终为True-您无需检查函数的结果

def check(fname, txt):
    with open(fname) as dataf:
        return any(txt in line for line in dataf)

if check('example.txt', 'blabla'):
    print "true"
else:
    print "false"

Two problems:

  1. Your function does not return anything; a function that does not explicitly return anything returns None (which is falsy)

  2. True is always True - you are not checking the result of your function

.

def check(fname, txt):
    with open(fname) as dataf:
        return any(txt in line for line in dataf)

if check('example.txt', 'blabla'):
    print "true"
else:
    print "false"

回答 7

如何在文件中搜索文本并返回在其中找到单词的文件路径。

import os
import re

class Searcher:
    def __init__(self, path, query):
        self.path   = path

        if self.path[-1] != '/':
            self.path += '/'

        self.path = self.path.replace('/', '\\')
        self.query  = query
        self.searched = {}

    def find(self):
        for root, dirs, files in os.walk( self.path ):
            for file in files:
                if re.match(r'.*?\.txt$', file) is not None:
                    if root[-1] != '\\':
                        root += '\\'           
                    f = open(root + file, 'rt')
                    txt = f.read()
                    f.close()

                    count = len( re.findall( self.query, txt ) )
                    if count > 0:
                        self.searched[root + file] = count

    def getResults(self):
        return self.searched

在Main()中

# -*- coding: UTF-8 -*-

import sys
from search import Searcher

path = 'c:\\temp\\'
search = 'search string'


if __name__ == '__main__':

    if len(sys.argv) == 3:
        # создаем объект поисковика и передаем ему аргументы
        Search = Searcher(sys.argv[1], sys.argv[2])
    else:
        Search = Searcher(path, search)

    # начать поиск
    Search.find()

    # получаем результат
    results = Search.getResults()

    # выводим результат
    print 'Found ', len(results), ' files:'

    for file, count in results.items():
        print 'File: ', file, ' Found entries:' , count

How to search the text in the file and Returns an file path in which the word is found (Как искать часть текста в файле и возвращять путь к файлу в котором это слово найдено)

import os
import re

class Searcher:
    def __init__(self, path, query):
        self.path   = path

        if self.path[-1] != '/':
            self.path += '/'

        self.path = self.path.replace('/', '\\')
        self.query  = query
        self.searched = {}

    def find(self):
        for root, dirs, files in os.walk( self.path ):
            for file in files:
                if re.match(r'.*?\.txt$', file) is not None:
                    if root[-1] != '\\':
                        root += '\\'           
                    f = open(root + file, 'rt')
                    txt = f.read()
                    f.close()

                    count = len( re.findall( self.query, txt ) )
                    if count > 0:
                        self.searched[root + file] = count

    def getResults(self):
        return self.searched

In Main()

# -*- coding: UTF-8 -*-

import sys
from search import Searcher

path = 'c:\\temp\\'
search = 'search string'


if __name__ == '__main__':

    if len(sys.argv) == 3:
        # создаем объект поисковика и передаем ему аргументы
        Search = Searcher(sys.argv[1], sys.argv[2])
    else:
        Search = Searcher(path, search)

    # начать поиск
    Search.find()

    # получаем результат
    results = Search.getResults()

    # выводим результат
    print 'Found ', len(results), ' files:'

    for file, count in results.items():
        print 'File: ', file, ' Found entries:' , count

回答 8

发现=错误

def check():
    datafile = file('example.txt')
    for line in datafile:
        if blabla in line:
            found = True
            break
    return found

if check():
    print "true"
else:
    print "false"

found = False

def check():
    datafile = file('example.txt')
    for line in datafile:
        if blabla in line:
            found = True
            break
    return found

if check():
    print "true"
else:
    print "false"

回答 9

如果用户要在给定的文本文件中搜索单词。

 fopen = open('logfile.txt',mode='r+')

  fread = fopen.readlines()

  x = input("Enter the search string: ")

  for line in fread:

      if x in line:

          print(line)

If user wants to search for the word in given text file.

 fopen = open('logfile.txt',mode='r+')

  fread = fopen.readlines()

  x = input("Enter the search string: ")

  for line in fread:

      if x in line:

          print(line)

回答 10

found = False
def check():
datafile = file('example.txt')
for line in datafile:
    if "blabla" in line:
        found = True
        break
return found

if check():
    print "found"
else:
    print "not found"
found = False
def check():
datafile = file('example.txt')
for line in datafile:
    if "blabla" in line:
        found = True
        break
return found

if check():
    print "found"
else:
    print "not found"

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