Release Notes

Version 0.11

This release focuses on fixing bugs related to uncommon HTTP/HTML scenarios and on improving the documentation.

Bug fixes

  • Constructing a Form instance from a bs4.element.Tag whose tag name is not form will now emit a warning, and may be deprecated in the future. [#228]
  • Breaking Change: LinkNotFoundError now derives from Exception instead of BaseException. While this will bring the behavior in line with most people’s expectations, it may affect the behavior of your code if you were heavily relying on this implementation detail in your exception handling. [#203]
  • Improve handling of button submit elements. Will now correctly ignore buttons of type button and reset during form submission, since they are not considered to be submit elements. [#199]
  • Do a better job of inferring the content type of a response if the Content-Type header is not provided. [#195]
  • Improve consistency of query string construction between MechanicalSoup and web browsers in edge cases where form elements have duplicate name attributes. This prevents errors in valid use cases, and also makes MechanicalSoup more tolerant of invalid HTML. [#158]

Version 0.10

Main changes:

  • Added StatefulBrowser.refresh() to reload the current page with the same request. [#188]
  • StatefulBrowser.follow_link, StatefulBrowser.submit_selected() and the new StatefulBrowser.download_link now sets the Referer: HTTP header to the page from which the link is followed. [#179]
  • Added method StatefulBrowser.download_link, which will download the contents of a link to a file without changing the state of the browser. [#170]
  • The selector argument of Browser.select_form can now be a bs4.element.Tag in addition to a CSS selector. [#169]
  • Browser.submit and StatefulBrowser.submit_selected accept a larger number of keyword arguments. Arguments are forwarded to requests.Session.request. [#166]

Internal changes:

  • StatefulBrowser.choose_submit will now ignore input elements that are missing a name-attribute instead of raising a KeyError. [#180]
  • Private methods Browser._build_request and Browser._prepare_request have been replaced by a single method Browser._request. [#166]

Version 0.9

Main changes:

  • We do not rely on BeautifulSoup’s default choice of HTML parser. Instead, we now specify lxml as default. As a consequence, the default setting requires lxml as a dependency.

  • Python 2.6 and 3.3 are no longer supported.

  • The GitHub URL moved from to @moy and @hemberger are now officially administrators of the project in addition to @hickford, the original author.

  • We now have a documentation site: The API is now fully documented, and we have included a tutorial, several more code examples, and a FAQ.

  • StatefulBrowser.select_form can now be called without argument, and defaults to "form" in this case. It also has a new argument, nr (defaults to 0), which can be used to specify the index of the form to select if multiple forms match the selection criteria.

  • We now use requirement files. You can install the dependencies of MechanicalSoup with e.g.:

    pip install -r requirements.txt -r tests/requirements.txt
  • The Form class was restructured and has a new API. The behavior of existing code is unchanged, but a new collection of methods has been added for clarity and consistency with the set method:

    • set_input deprecates input
    • set_textarea deprecates textarea
    • set_select is new
    • set_checkbox and set_radio together deprecate check (checkboxes are handled differently by default)
  • A new Form.print_summary method allows you to write browser.get_current_form().print_summary() to get a summary of the fields you need to fill-in (and which ones are already filled-in).

  • The Form class now supports selecting multiple options in a <select multiple> element.

Bug fixes

  • Checking checkboxes with browser["name"] = ("val1", "val2") now unchecks all checkbox except the ones explicitly specified.
  • StatefulBrowser.submit_selected and now reset __current_page to None when the result is not an HTML page. This fixes a bug where __current_page was still the previous page.
  • We don’t error out anymore when trying to uncheck a box which doesn’t have a checkbox attribute.
  • Form.new_control now correctly overrides existing elements.

Internal changes

  • The testsuite has been further improved and reached 100% coverage.
  • Tests are now run against the local version of MechanicalSoup, not against the installed version.
  • Browser.add_soup will now always attach a soup-attribute. If the response is not text/html, then soup is set to None.
  • Form.set(force=True) creates an <input type=text ...> element instead of an <input type=input ...>.

Version 0.8

Main changes:

  • Browser and StatefulBrowser can now be configured to raise a LinkNotFound exception when encountering a 404 Not Found error. This is activated by passing raise_on_404=True to the constructor. It is disabled by default for backward compatibility, but is highly recommended.
  • Browser now has a __del__ method that closes the current session when the object is deleted.
  • A Link object can now be passed to follow_link.
  • The user agent can now be customized. The default includes MechanicalSoup and its version.
  • There is now a direct interface to the cookiejar in *Browser classes ((set|get)_cookiejar methods).
  • This is the last MechanicalSoup version supporting Python 2.6 and 3.3.

Bug fixes:

  • We used to crash on forms without action=”…” fields.
  • The choose_submit method has been fixed, and the btnName argument of StatefulBrowser.submit_selected is now a shortcut for using choose_submit.
  • Arguments to open_relative were not properly forwarded.

Internal changes:

Version 0.7

see Git history, no changelog sorry.