You can also use Js2Py which is written in pure python and is able to both execute and translate javascript to python. Supports virtually whole JavaScript even labels, getters, setters and other rarely used features.

import js2py

js = """
function escramble_758(){
var a,b,c
a='+1 '
b='84-'
a+='425-'
b+='7450'
c='9'
document.write(a+c+b)
}
escramble_758()
""".replace("document.write", "return ")

result = js2py.eval_js(js)  # executing JavaScript and converting the result to python string 

Advantages of Js2Py include portability and extremely easy integration with python (since basically JavaScript is being translated to python).

To install:

pip install js2py

download using requests and extract the filename using os.path.basename()

import os

for js_file in script_files:
    fileName = os.path.basename(js_file)
    text = requests.get(js_file).text
    with open(fileName, 'w', encoding="utf-8") as f:
        f.write(text)

for css_file in css_files:
    fileName = os.path.basename(css_file)
    text = requests.get(js_file).text
    with open(fileName, 'w', encoding="utf-8") as f:
        f.write(text)
        

After some more research on that link, I came up with this. You can definitely use mechanize to do it.

import mechanize

def getJSVariableValue(content, variable):
    value_start_index = content.find(variable)
    value_start_index = content.find('"', value_start_index) + 1

    value_end_index = content.find('"', value_start_index)

    value = content[value_start_index:value_end_index]
    return value

def getChartReport(url):
    br = mechanize.Browser()
    resp = br.open(url)
    content = resp.read()
    br.select_form(name = 'apiForm')
    br.form.set_all_readonly(False)
    br.form['rowids'] = getJSVariableValue(content, 'document.apiForm.rowids.value')
    br.form['annot'] = getJSVariableValue(content, 'document.apiForm.annot.value')
    br.form.action = 'http://david.abcc.ncifcrf.gov/' + getJSVariableValue(content, 'document.apiForm.action')

    print br.form['rowids']
    print br.form['annot']

    br.submit()

    resp = br.follow_link(text_regex=r'Download File')
    content = resp.read()
    f = open('output.txt', 'w')
    f.write(content)


url = 'http://david.abcc.ncifcrf.gov/api.jsp?type=GENBANK_ACCESSION&ids=CP000010,CP000125,CP000124,CP000124,CP000124,CP000124&tool=chartReport&annot=KEGG_PATHWAY'
chart_output = getChartReport(url)