How to delete specific strings from a file?

Question

I have a data file (unstructured, messy file) from which I have to scrub specific list of strings (delete strings).

Here is what I am doing but with no result:

Answer 1

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()