RegExp: returning 2nd loop in new document

[syoung]

Hello, I am new to this forum. I joined so that I could ask for help with this program. First, I will detail what it does.

I get these search files that look a bit like this:
!sfshine Robert Silverberg & Karen Haber (ed) - Science Fiction-The Best of 2001.epub ::INFO:: 344.3KB
!sfshine Robert Silverberg & Karen Haber (ed) - Science Fiction-The Best of 2001.zip ::INFO:: 373.7KB
!sfshine Robert Silverberg & Karen Haber (ed) - Science Fiction-The Best of 2002.epub ::INFO:: 493.9KB
!sfshine Robert Silverberg & Karen Haber (ed) - Science Fiction-The Best of 2002.mobi ::INFO:: 546.6KB
!sfshine Robert Silverberg & Karen Haber (ed) - Science Fiction-The Best of 2002.zip ::INFO:: 297.2KB

I only have a use for certain types of files. Now, I can get my script to filter one or several at a time by using a for in loop. I thought that if I added a second loop, I could get them sorted into different piles. So, here is the code:
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import re

# input the name of the file
input_file_name = input("Enter file name: ")
input_file_name = input_file_name + ".txt"
input_open = open(input_file_name)

# create new file name
file_type_removed = input_file_name[:-4] #  removes .txt from input file name
add_modified_to_new_file = "_modified.txt" #  creates the end part of the new file name
new_text = file_type_removed + add_modified_to_new_file #  puts the file extension and modified to the new file

new_file_create = open(new_text, "w+") # should create a new file with this name

#  finds all the lines with mobi in them and writes those lines to the new file
for line in input_open.readlines():
    if re.search('mobi|azw', line):
        new_file_create.write(line)

#  This second loop will not run or return the results as I expected. Only the first loop 
#  returns a text file with the expected results. I would like to understand why and how 
#  I might fix it.
for line in input_open.readlines():
    if re.search('pdf', line):
        new_file_create.write(line)


# Close the files
new_file_create.close()
input_open.close()

***********************************
I also have a second question that I have been thinking about: I have thought about building a library of authors that
sometimes I want to search for. So, I wondered if using a similar formula to what I have already but as a function where
the loop iterates through the dictionary looking for and returning lines which contain the name of the given author. Is
that a valid way of going about it, or should I be seeking a different path?

Any help is appreciated,
Steven