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I need to look for a list of words in a document. However, when I run my code it seems to only iterate over the first word. I know it has something to do with my while(s) loop, but I just can't seem to get it to work. Also, yes the words are in the document.

How do I apply the code to each word in the list?

file = open('DOG2.txt', 'r')
word = ['cat','dog','Yellow']
s = " "
count=1
for p in word:
    while(s):
      s = file.readline()
      L = s.split()
      if p in L:
          print("Line Number:",file.name,p,count,":",s)

      count+=1
Gino Mempin
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B MS
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  • Think carefully about the logic of the code. Which way do we want it to work: do we read a line from the file and test each `word` against that line, before moving on to the next line? Or should we take a word from the `word` list and test each line against that word, before moving on to the next word? Therefore, which loop should be the inner loop, and which loop should be the outer loop? – Karl Knechtel Oct 14 '22 at 23:15
  • (If the question is "Why doesn't it work the other way around?", then that is because `file.readline` will not start over at the beginning of the file when the outer loop starts again; do you understand why? We have a duplicate for that question: https://stackoverflow.com/questions/3906137) – Karl Knechtel Oct 14 '22 at 23:16
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    Does this answer your question? [Why can't I call read() twice on an open file?](https://stackoverflow.com/questions/3906137/why-cant-i-call-read-twice-on-an-open-file) – Rahul K P Oct 14 '22 at 23:26
  • While the duplicate link mentions `read()`, it applies to `readline()` and `readlines()` as well, since this is all about doing the same file I/O operation on the same file. – Gino Mempin Oct 14 '22 at 23:37

2 Answers2

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The main issue was, file operation is a stream operation. Each read operation is monotony increases unless you manually reset it.
To fix your code, at the end of each for p loop, you need to insert file.seek(0).

Here is a better solution that only scan the file once (instead of 3 times):

word = ['cat','dog','Yellow']
count=0
with open('DOG2.txt', 'r') as file:
    for line in file:
        count+=1
        for w in word:
            if w in line.strip().split():
                print("LineNumber:{} {} {} : {}".format(file.name, w, count, line), end="")

Here is an even better solution to enhance the performance when the file and word size are large.

word = {'cat','dog','Yellow'}
count=0
with open('DOG2.txt', 'r') as file:
    for line in file:
        count+=1
        lset = set(line.strip().split())
        if bool(word & lset):
            print("LineNumber:{} {} : {}".format(file.name, count, line), end="")
Xin Cheng
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When using readline python keeps track of which line it has to read. So, after reading the last line, it does not start from the beginning and returns an empty string '' on calling readline (which also evaluates to false in loop conditions).

In your code, you finish all the lines during the check for the first word. So, what is the solution? Read the line first and check all the words in the L list that you have created. A fix would probably be something like this.

file = open('DOG2.txt', 'r')
word = ['cat','dog','Yellow']
s = " "
while s:
    s = file.readline()
    L = s.split()
    for p in word:
        if p in L:
            print("Line Number:",file.name,p,count,":",s)
    count += 1

Recommendation: You can use for loop to iterate over the lines of a file. For example:

f = open('fn.txt', 'r')
for line in f:
   ...
AliBaharni97
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