如何在没有外部模块的情况下清理 Python 3 文本块？

Question

Recently was set a hackerrank to do and I couldn't get a block of text to properly be sanitized from tags without breaking the text in Python 3.

Two example inputs were provided (below) and the challenge was to clear them to make them safe normal text blocks. Time to complete the challenge is over but I'm confused how I got something so simple so wrong. Any help on how I should've gone about it would be appreciated.

Test input one

It is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. <script>
var y=window.prompt("Hello")
window.alert(y)
</script>Contrary to popular belief, Lorem Ipsum is not simply random text. It has roots in a piece of classical Latin literature from 45 BC, making it over 2000 years old. Richard McClintock, a Latin professor at Hampden-Sydney College in Virginia, looked up one of the more obscure Latin words, consectetur, from a Lorem Ipsum passage.

Test input two

In-text references or citations are used to acknowledge the work or ideas of others. They are placed next to the text that you have paraphrased or quoted, enabling the reader to differentiate between your writing and other people’s work.  The full details of your in-text references, <script language="JavaScript">
document.write("Page. Last update:" + document.lastModified); </script>When quoting directly from the source include the page number if available and place quotation marks around the quote, e.g. 
The World Health Organisation defines driver distraction ‘as when some kind of triggering event external to the driver results in the driver shifting attention away from the driving task’.

Test proposed output 1

It is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. Contrary to popular belief, Lorem Ipsum is not simply random text. It has roots in a piece of classical Latin literature from 45 BC, making it over 2000 years old. Richard McClintock, a Latin professor at Hampden-Sydney College in Virginia, looked up one of the more obscure Latin words, consectetur, from a Lorem Ipsum passage.

Test proposed output 2

  In-text references or citations are used to acknowledge the work or ideas of others. They are placed next to the text that you have paraphrased or quoted, enabling the reader to differentiate between your writing and other people’s work. The full details of your in-text references, When quoting directly from the source include the page number if available and place quotation marks around the quote, e.g. The World Health Organisation defines driver distraction ‘as when some kind of triggering event external to the driver results in the driver shifting attention away from the driving task’.

Thanks in advance!

EDIT (Using @YakovDan's sanitisation) : The code:

def sanitize(inp_str):

    ignore_flag =False
    close_tag_count = 0


    out_str =""
    for c in inp_str:
        if not ignore_flag:
           if c == '<':
               close_tag_count=2
               ignore_flag=True
           else:
               out_str+=c
        else:
            if c == '>':
                close_tag_count-=1

            if close_tag_count == 0:
                ignore_flag=False


    return out_str

inp=input()
print(sanitize(inp))

The input:

It is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. <script>
 var y=window.prompt("Hello")
 window.alert(y)
 </script>Contrary to popular belief, Lorem Ipsum is not simply random text. It has roots in a piece of classical Latin literature from 45 BC, making it over 2000 years old. Richard McClintock, a Latin professor at Hampden-Sydney College in Virginia, looked up one of the more obscure Latin words, consectetur, from a Lorem Ipsum passage.

The output:

It is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy.

What the output should be:

It is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy.Contrary to popular belief, Lorem Ipsum is not simply random text. It has roots in a piece of classical Latin literature from 45 BC, making it over 2000 years old. Richard McClintock, a Latin professor at Hampden-Sydney College in Virginia, looked up one of the more obscure Latin words, consectetur, from a Lorem Ipsum passage.

Answer 1

In general, regular expressions are the wrong tool for parsing HTML tags ( see here ), but it will work for this job since the tags are simple - if you have non-regular (tags which don't have closing tags etc.) inputs, it will fail.

That being said, for this two examples, you can use this regex :

<.*?>.*?<\s*?\/.*?>

Implemented in Python:

import re
s = one of your long strings
r = re.sub('<.*?>.*?<\s*?\/.*?>', '', s, flags=re.DOTALL)
print(r)

which gives the expected results (too long-winded to copy them in!).

Answer 2

Here's a way to do this without regex.

def sanitize(inp_str):

    ignore_flag =False
    close_tag_count = 0


    out_str =""
    for c in inp_str:
        if not ignore_flag:
           if c == '<':
               close_tag_count=2
               ignore_flag=True
           else:
               out_str+=c
        else:
            if c == '>':
                close_tag_count-=1

            if close_tag_count == 0:
                ignore_flag=False


     return out_str

This should do it (up to assumptions about tags)