How to search for a string in text files

Question

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

User · Answer

Two problems    Your function does not return anything  a function that does not explicitly return anything returns None  which is falsy  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

User · Answer

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

User · Answer

How to search the text in the file and Returns an file path in which the word is found                                                                                          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  gt  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                                                                       Search   Searcher sys argv 1   sys argv 2       else          Search   Searcher path  search                          Search find                                 results   Search getResults                                print  Found    len results     files        for file  count in results items            print  File     file    Found entries     count

User · Answer

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

User · Answer

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  lt Line  num  gt   line                else                  print f  gt   word  not found        if   name         main           file to process     path to file        string to find   input         word find file to process  string to find

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

[python] How to search for a string in text files?

Examples related to python