Evaluate Previous line in a Text file with Python-CodePudding

I am creating a program to edit a text file using the fileinput library. What I want to do is search every line in the text file for a certain string and delete it. But I also want to delete the line above if it contains a different but defined string.

For example, if I want to delete every line that contains the word "dog" but I also want to the delete the line above if it contains the word "cat".

The original text would be:

I enjoy animals.
I have 2 fish.
I also have a cat.
I also have a dog.
I do not have a gerbil.
My dog stays inside.
The fish have a tank.
The cat goes outside.
My animals are awesome.

The result I want to be:

I enjoy animals.
I have 2 fish.
I do not have a gerbil.
The fish have a tank.
The cat goes outside.
My animals are awesome.

So I am deleting all the lines with "dog" and also the line with "cat" that is above the line with "dog" but not the line with "cat" that doesn't have a line with "dog" after it.

Any thoughts or suggestions?

CodePudding user response：

def dog(line):
    if "dog" in line:
        return True
    else:
        return False

def cat(line):
    if "cat" in line:
        return True
    else:
        return False


saved_lines=[]
last_line=""
for line in lines:
    if dog(line) is False: # Not a dog line
        saved_lines.append(l)

    else:
        if cat(last_line) is True:
            saved_lines=saved_lines[:-1] # Delete the last line from the  saved list
    last_line = line  # At end of loop, refresh last_line to value of current line

Rather than performing a delete, here the code selectively copies content into saved_lines. If a line has a "dog" then it wont be copied. If a line does have a "dog", then the last line saved is a candidate for removal, on detection of a "cat".

Your content should be saved in the saved_lines list variable.

The downside of this method is if your starting list is huge, then you're very nearly doubling it by saving a selective copy. But chances are you'll be ok.

CodePudding user response：

Read the file and store it in a list and do this, and write back to another file.

data = ['I enjoy animals.',
 'I have 2 fish.',
 'I also have a cat.',
 'I also have a dog.',
 'I do not have a gerbil.',
 'My dog stays inside.',
 'The fish have a tank.',
 'The cat goes outside.',
 'My animals are awesome.']

word_list = ['cat', 'dog']
result = [item for item in data if not any(word in item for word in word_list)]

# result
['I enjoy animals.',
 'I have 2 fish.',
 'I do not have a gerbil.',
 'The fish have a tank.',
 'My animals are awesome.']