can someone give me an idea how to extract information for text such as invoice bills using natural language processing suppose i have text file with invoice details in it . I want to extract only some information based on my certain condition such as Mobile - 25,000 and quantity - 1 i want to extract only mobile and quantity based information and store it in text file.Can someone give me an idea how to do this.
You might be looking for regex. With this you can parse the text based on your specified search patterns.

Some info:
https://en.wikipedia.org/wiki/Regular_expression

With python you can follow this documentation in order to build your regex expressions:
https://docs.python.org/3.8/library/re.html