CODEWITHSUNDEEP
python
HankSmackHood
HankSmackHood

Reputation: 4873

How to search for a string in text files?

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"

Upvotes: 239

Views: 1091788

Answers (14)

phidelity
phidelity

Reputation: 57

things to keep in mind if you are actively updating/ interacting with the information in the file. i) The read in file will not contain appended data that you could be searching for.

   my_file = open('path/to/my_file', a+)# in append plus mode (read and write)
   my_file.write("foo") #
   if my_file.read().find("foo") !=-1: # returns -1
       print("this condition is not met")
   # you would have to read the file in again
   my_file = open('path/to/my_file', a+)
   #now the appended text is in active memory

ii) the readlines is an iterable and will be spent in the following case:

# I was merging text from two files
original_exif = open(my_file)
donor_file - open(my_file)
# this list is full
original_lines = original_exif.readlines()
for line in original_exif:
    print(line)
    temp_exif.write(line)
    print(f"where are we in the temp_exif:\n {temp_exif.tell()}")



print(f"original lines full list\n {original_lines}")
original_lines = original_exif.readlines()
print(f"original lines declared after being iterated through and the list is now empty\n {original_lines}")

I hope its ok to post here. It's not directly anwering the search post but these details can make a difference and they both caught me while attempting a script to merge text from combinations of files.

Upvotes: 1

amitnaruto
amitnaruto

Reputation: 331

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_to_search_into', 'r').read().find('searched_string')

Upvotes: 33

Baris Ozensel
Baris Ozensel

Reputation: 463

"found" needs to be created as global variable in the function as "if else" statement is out of the function. You also don't need to use "break" to break the loop code. The following should work to find out if the text file has desired string.

with open('text_text.txt') as f:
    datafile = f.readlines()


def check():
    global found
    found = False
    for line in datafile:
        if 'the' in line:
            found = True


check()

if found == True:
    print("True")
else:
    print("False")

Upvotes: 0

mana
mana

Reputation: 129

Here's another. Takes an absolute file path and a given string and passes it to word_find(), uses readlines() method on the given file within the enumerate() method which gives an iterable count as it traverses line by line, in the end giving you the line with the matching string, plus the given line number. Cheers.

  def word_find(file, word):
    with open(file, 'r') as target_file:
        for num, line in enumerate(target_file.readlines(), 1):
            if str(word) in line:
                print(f'<Line {num}> {line}')
            else:
                print(f'> {word} not found.')


  if __name__ == '__main__':
      file_to_process = '/path/to/file'
      string_to_find = input()
      word_find(file_to_process, string_to_find)

Upvotes: 0

bruh
bruh

Reputation: 41

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"

Upvotes: 0

Steven
Steven

Reputation: 28656

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):

Upvotes: 517

Harshan Gowda
Harshan Gowda

Reputation: 177

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)

Upvotes: 2

amccormack
amccormack

Reputation: 13927

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')

Upvotes: 38

Coco
Coco

Reputation: 906

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.

Upvotes: 6

user2710152
user2710152

Reputation:

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

Upvotes: 2

karlcow
karlcow

Reputation: 6972

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"

Upvotes: 1

Hugh Bothwell
Hugh Bothwell

Reputation: 56624

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"

Upvotes: 2

Sam Dolan
Sam Dolan

Reputation: 32532

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"

Upvotes: 4

Jeffrey Greenham
Jeffrey Greenham

Reputation: 1432

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!

Upvotes: 16

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