How to delete specific strings from a file?

The readlines method returns a list of lines, not words, so your code would only work where one of your words is on a line by itself.

Since files are iterators over lines this can be done much easier:

infile = "messy_data_file.txt"
outfile = "cleaned_file.txt"

delete_list = ["word_1", "word_2", "word_n"]
with open(infile) as fin, open(outfile, "w+") as fout:
    for line in fin:
        for word in delete_list:
            line = line.replace(word, "")
        fout.write(line)

To remove the string within the same file, I used this code

f = open('./test.txt','r')
a = ['word1','word2','word3']
lst = []
for line in f:
    for word in a:
        if word in line:
            line = line.replace(word,'')
    lst.append(line)
f.close()
f = open('./test.txt','w')
for line in lst:
    f.write(line)
f.close()

Based on your comment "I am double clicking the .py file. It seems to invoke the python application which disappears after a couple of seconds. I dont get any error thought" I believe your issue is the script is not finding the input file. That is also why you are not getting any output. When you double click on it... I actually can't recall where the interpreter is going to look but I think it's where the python.exe is installed.

Use a fully qualified path like so.

# Depends on your OS
infile = r"C:\tmp\messy_data_file.txt"
outfile = r"C:\tmp\cleaned_file.txt"

infile = r"/etc/tmp/messy_data_file.txt"
outfile = r"/etc/tmp/cleaned_file.txt"

Also, for your sanity, run it from the command-line instead of double clicking. It'll be much easier to catch errors/output.

To the OP, Ross Patterson's method above works perfectly for me, i.e.

infile = "messy_data_file.txt"
outfile = "cleaned_file.txt"

delete_list = ["word_1", "word_2", "word_n"]
fin = open(infile)
fout = open(outfile, "w+")
for line in fin:
    for word in delete_list:
        line = line.replace(word, "")
    fout.write(line)
fin.close()
fout.close()

Example:

I have a file named messy_data_file.txt that includes the following words (animals), not necessarily on the same line. Like this:

Goat
Elephant
Horse Donkey Giraffe
Lizard
Bird
Fish

When I modify the code to read (actually just adding the words to delete to the "delete_list" line):

infile = "messy_data_file.txt"
outfile = "cleaned_file.txt"

delete_list = ["Donkey", "Goat", "Fish"]
fin = open(infile)
fout = open(outfile, "w+")
for line in fin:
    for word in delete_list:
       line = line.replace(word, "")
    fout.write(line)
fin.close()
fout.close()

The resulting "cleaned_file.txt" looks like this:

Elephant
Horse  Giraffe
Lizard
Bird

There is a blank line where "Goat" used to be (where, oddly, removing "Donkey" did not) but for my purposes, this works fine.

I also add input("Press Enter to exit...") the the very end of the code to keep the command line window from opening and slamming shut on me when I'm double-clicking the remove_text.py file to run it, but take note that you'll catch no errors this way.

To do that I run it from the command line (where C:\Just_Testing is the directory where all my files are, i.e. remove_text.py and messy_text.txt) like this:

C:\Just_Testing\>py remove_text.py 

or

C:\Just_Testing>python remove_text.py 

works exactly the same.

Of course, like when writing HTML, I guess it never hurts to use a fully qualified path when running py or python from somewhere other than the directory you happen to be sitting in, such as:

C:\Windows\System32\>python C:\Users\Me\Desktop\remove_text.py

Of course in the code it would be:

infile = "C:\Users\Me\Desktop\messy_data_file.txt"
outfile = "C:\Users\Me\Desktop\cleaned_file.txt"

Be careful to use the same fully qualified path to place your newly created cleaned_file.txt in or it will be created wherever you may be and that could cause confusion when looking for it.

Personally, I have the PATH in my Environment Variables set to point to all my Python installs i.e. C:\Python3.5.3, C:\Python2.7.13, etc. so I can run py or python from anywhere.

Anyway, I hope making fine-tuning adjustments to this code from Mr. Patterson can get you exactly what you need. :)

.

Maybe you can add encoding='utf-8' in your fin and fout variables. Here is the modified one you may want to use:

fin=open(infile,"", encoding='utf-8')
fout = open(outfile,"w+", encoding='utf-8')

This(adding utf-8) mostly occurs on the OS Windows. Also for reading, writing, and appending the file, this usually isn't a problem but for advanced things to do a file like replacing text in there, etc then you should do this.

Hope this helps you.

The code below just gets the old data and checks if the string doesnt contain the string you doesnt want then continues. (this also works if you want to remove empty lines)

str = []
with open("file.txt", "r+") as f:
    for i in f.readlines():
        str.append(i)
with open("file.txt", "w") as f:
    for i in str:
        if i != "The string you want to remove":
           f.write(i)