Python 3, filling out a form with request (library) returns same page HTML without inputting parameters

The first observation is that you seem to be using a get request in your example code instead of a post request.

<form action="taa_search.cfm" method="post" ...>                              ^^^^^^^^^^^^^

After changing to a post request, I was still getting the same results as you though (html from the main search form page). After a bit of experimentation, I seem to be able to get the proper html results by adding a referer to the header.

Here is the code (I only commented out the writing to file part for example purposes):

import requestsBASE_URL = 'https://www.doleta.gov/tradeact/taa'def get_case_decision(case_number):    headers = {        'referer': '{}/taa_search_form.cfm'.format(BASE_URL)    }    payload = {        'form_name': 'number_search',        'input': case_number    }    r = requests.post(        '{}/taa_search.cfm'.format(BASE_URL),        data=payload,        headers=headers    )    r.raise_for_status()    return r.text    # with open('requests_results_{}.html'.format(case_number), 'wb') as f:    #     f.write(r.content)

Testing:

>>> result = get_case_decision(10000)>>> 'MODINE MFG. COMPANY' in resultTrue>>> '9/12/1980' in resultTrue>>> result = get_case_decision(10001)>>> 'MUSKIN CORPORATION' in resultTrue>>> '2/27/1981' in resultTrue

Since you mentioned that you need to perform this ~10,000 times, you will probably want to look into using requests.Session as well.