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资源说明：ClientForm python module by John J. Lee





  
  
  
  
  ClientForm
  
  






ClientForm






ClientForm is a Python module for handling HTML forms on the client
side, useful for parsing HTML forms, filling them in and returning the
completed forms to the server.  It developed from a port of Gisle Aas'
Perl module HTML::Form, from the libwww-perl library, but the
interface is not the same.


Simple working example:


from urllib2 import urlopen
from ClientForm import ParseResponse

response = urlopen("http://wwwsearch.sourceforge.net/ClientForm/example.html")
forms = ParseResponse(response, backwards_compat=False)
form = forms[0]
print form
form["comments"] = "Thanks, Gisle"

# form.click() returns a urllib2.Request object
# (see HTMLForm.click.__doc__ if you don't have urllib2)
print urlopen(form.click()).read()




A more complicated working example (Note: this
example makes use of the ClientForm 0.2 API; refer to the README.html
file in the latest 0.1 release for the corresponding code for that
version.):



import ClientForm
import urllib2
request = urllib2.Request(
    "http://wwwsearch.sourceforge.net/ClientForm/example.html")
response = urllib2.urlopen(request)
forms = ClientForm.ParseResponse(response, backwards_compat=False)
response.close()
## f = open("example.html")
## forms = ClientForm.ParseFile(f, "http://example.com/example.html",
##                              backwards_compat=False)
## f.close()
form = forms[0]
print form  # very useful!

# A 'control' is a graphical HTML form widget: a text entry box, a
# dropdown 'select' list, a checkbox, etc.

# Indexing allows setting and retrieval of control values
original_text = form["comments"]  # a string, NOT a Control instance
form["comments"] = "Blah."

# Controls that represent lists (checkbox, select and radio lists) are
# ListControl instances.  Their values are sequences of list item names.
# They come in two flavours: single- and multiple-selection:
form["favorite_cheese"] = ["brie"]  # single
form["cheeses"] = ["parmesan", "leicester", "cheddar"]  # multi
#  equivalent, but more flexible:
form.set_value(["parmesan", "leicester", "cheddar"], name="cheeses")

# Add files to FILE controls with .add_file().  Only call this multiple
# times if the server is expecting multiple files.
#  add a file, default value for MIME type, no filename sent to server
form.add_file(open("data.dat"))
#  add a second file, explicitly giving MIME type, and telling the server
#   what the filename is
form.add_file(open("data.txt"), "text/plain", "data.txt")

# All Controls may be disabled (equivalent of greyed-out in browser)...
control = form.find_control("comments")
print control.disabled
#  ...or readonly
print control.readonly
#  readonly and disabled attributes can be assigned to
control.disabled = False
#  convenience method, used here to make all controls writable (unless
#   they're disabled):
form.set_all_readonly(False)

# A couple of notes about list controls and HTML:

# 1. List controls correspond to either a single SELECT element, or
# multiple INPUT elements.  Items correspond to either OPTION or INPUT
# elements.  For example, this is a SELECT control, named "control1":

#    <select name="control1">
#     <option>foo</option>
#     <option value="1">bar</option>
#    </select>

# and this is a CHECKBOX control, named "control2":

#    <input type="checkbox" name="control2" value="foo" id="cbe1">
#    <input type="checkbox" name="control2" value="bar" id="cbe2">

# You know the latter is a single control because all the name attributes
# are the same.

# 2. Item names are the strings that go to make up the value that should
# be returned to the server.  These strings come from various different
# pieces of text in the HTML.  The HTML standard and the ClientForm
# docstrings explain in detail, but playing around with an HTML file,
# ParseFile() and 'print form' is very useful to understand this!

# You can get the Control instances from inside the form...
control = form.find_control("cheeses", type="select")
print control.name, control.value, control.type
control.value = ["mascarpone", "curd"]
# ...and the Item instances from inside the Control
item = control.get("curd")
print item.name, item.selected, item.id, item.attrs
item.selected = False

# Controls may be referred to by label:
#  find control with label that has a *substring* "Cheeses"
#  (eg., a label "Please select a cheese" would match).
control = form.find_control(label="select a cheese")

# You can explicitly say that you're referring to a ListControl:
#  set value of "cheeses" ListControl
form.set_value(["gouda"], name="cheeses", kind="list")
#  equivalent:
form.find_control(name="cheeses", kind="list").value = ["gouda"]
#  the first example is also almost equivalent to the following (but
#  insists that the control be a ListControl -- so it will skip any
#  non-list controls that come before the control we want)
form["cheeses"] = ["gouda"]
# The kind argument can also take values "multilist", "singlelist", "text",
# "clickable" and "file":
#  find first control that will accept text, and scribble in it
form.set_value("rhubarb rhubarb", kind="text", nr=0)
#  find, and set the value of, the first single-selection list control
form.set_value(["spam"], kind="singlelist", nr=0)

# You can find controls with a general predicate function:
def control_has_caerphilly(control):
    for item in control.items:
        if item.name == "caerphilly": return True
form.find_control(kind="list", predicate=control_has_caerphilly)

# HTMLForm.controls is a list of all controls in the form
for control in form.controls:
    if control.value == "inquisition": sys.exit()

# Control.items is a list of all Item instances in the control
for item in form.find_control("cheeses").items:
    print item.name

# To remove items from a list control, remove it from .items:
cheeses = form.find_control("cheeses")
curd = cheeses.get("curd")
del cheeses.items[cheeses.items.index(curd)]
# To add items to a list container, instantiate an Item with its control
# and attributes:
# Note that you are responsible for getting the attributes correct here,
# and these are not quite identical to the original HTML, due to
# defaulting rules and a few special attributes (e.g. Items that represent
# OPTIONs have a special "contents" key in their .attrs dict).  In future
# there will be an explicitly supported way of using the parsing logic to
# add items and controls from HTML strings without knowing these details.
ClientForm.Item(cheeses, {"contents": "mascarpone",
                          "value": "mascarpone"})

# You can specify list items by label using set/get_value_by_label() and
# the label argument of the .get() method.  Sometimes labels are easier to
# maintain than names, sometimes the other way around.
form.set_value_by_label(["Mozzarella", "Caerphilly"], "cheeses")

# Which items are present, selected, and successful?
#  is the "parmesan" item of the "cheeses" control successful (selected
#   and not disabled)?
print "parmesan" in form["cheeses"]
#  is the "parmesan" item of the "cheeses" control selected?
print "parmesan" in [
    item.name for item in form.find_control("cheeses").items if item.selected]
#  does cheeses control have a "caerphilly" item?
print "caerphilly" in [item.name for item in form.find_control("cheeses").items]

# Sometimes one wants to set or clear individual items in a list, rather
# than setting the whole .value:
#  select the item named "gorgonzola" in the first control named "cheeses"
form.find_control("cheeses").get("gorgonzola").selected = True
# You can be more specific:
#  deselect "edam" in third CHECKBOX control
form.find_control(type="checkbox", nr=2).get("edam").selected = False
#  deselect item labelled "Mozzarella" in control with id "chz"
form.find_control(id="chz").get(label="Mozzarella").selected = False

# Often, a single checkbox (a CHECKBOX control with a single item) is
# present.  In that case, the name of the single item isn't of much
# interest, so it's a good idea to check and uncheck the box without
# using the item name:
form.find_control("smelly").items[0].selected = True  # check
form.find_control("smelly").items[0].selected = False  # uncheck

# Items may be disabled (selecting or de-selecting a disabled item is
# not allowed):
control = form.find_control("cheeses")
print control.get("emmenthal").disabled
control.get("emmenthal").disabled = True
#  enable all items in control
control.set_all_items_disabled(False)

request2 = form.click()  # urllib2.Request object
try:
    response2 = urllib2.urlopen(request2)
except urllib2.HTTPError, response2:
    pass

print response2.geturl()
print response2.info()  # headers
print response2.read()  # body
response2.close()






All of the standard control types are supported: TEXT,
PASSWORD, HIDDEN, TEXTAREA,
ISINDEX, RESET, BUTTON (INPUT
TYPE=BUTTON and the various BUTTON types),
SUBMIT, IMAGE, RADIO,
CHECKBOX, SELECT/OPTION and
FILE (for file upload).  Both standard form encodings
(application/x-www-form-urlencoded and
multipart/form-data) are supported.


The module is designed for testing and automation of web
interfaces, not for implementing interactive user agents.


Security note: Remember that any passwords you store in
HTMLForm instances will be saved to disk in the clear if you
pickle them (directly or indirectly).  The simplest solution to this is to
avoid pickling HTMLForm objects.  You could also pickle before
filling in any password, or just set the password to "" before
pickling.


Python 2.0 or above is required.  To run the tests, you need the
unittest module (from PyUnit).  unittest is a
standard library module with Python 2.1 and above.


For full documentation, see the docstrings in ClientForm.py.


Note: this page describes the 0.2 (stable release)
interface.  See here for the
old 0.1 interface. 




Parsers



ClientForm contains two parsers.  See the FAQ entry on
XHTML for details.


mxTidy or µTidylib can be useful for dealing with
bad HTML.


I think it would be nice to have an implementation of ClientForm based on BeautifulSoup
(i.e. all methods and attributes implemented using the BeautifulSoup API),
since that module does tolerant HTML parsing with a nice API for doing
non-forms stuff.  (I'm not about to do this, though.  For anybody interested in
doing this, note that the ClientForm tests would need making
constructor-independent first.)




Backwards-compatibility mode



ClientForm 0.2 includes three minor backwards-incompatible interface
changes from version 0.1.


To make upgrading from 0.1 easier, and to allow me to stop supporting
version 0.1 sooner, version 0.2 contains support for operating in a
backwards-compatible mode, under which code written for 0.1 should work without
modification.  This is done on a per-HTMLForm basis via the
.backwards_compat attribute, but for convenience the
ParseResponse() and ParseFile() factory functions accept
backwards_compat arguments.  These backwards-compatibility
features will be removed in version 0.3.  The default is to operate in
backwards-compatible mode.  To run with backwards compatible mode turned
OFF (strongly recommended):


from urllib2 import urlopen
from ClientForm import ParseResponse
forms = ParseResponse(urlopen("http://example.com/"), backwards_compat=False)
# ...




The backwards-incompatible changes are:


    

  • Ambiguous specification of controls or items now results in
AmbiguityError.  If you want the old behaviour, explicitly pass
nr=0 to indicate you want the first matching control or item.


  • Item label matching is now done by substring, not by strict
string-equality (but note leading and trailing space is always stripped).
(Control label matching is always done by substring.)


  • Handling of disabled list items has changed.  First, note that handling
of disabled list items in 0.1 (and in 0.2's backwards-compatibility mode!) is
buggy: disabled items are successful (ie. disabled item names are sent back to
the server).  As a result, there was no distinction to be made between
successful items and selected items.  In 0.2, the bug is fixed, so this is no
longer the case, and it is important to note that list controls'
.value attribute contains only the successful item names;
items that are selected  but not successful (because disabled) are not
included in .value.  Second, disabled list items may no longer be
deselected: AttributeError is raised in 0.2, whereas deselection was allowed in
0.1.  The bug in 0.1 and in 0.2's backwards-compatibility mode will not be
fixed, to preserve compatibility and to encourage people to upgrade to the new
0.2 backwards_compat=False behaviour.  




Credits



Apart from Gisle Aas for allowing the original port from
libwww-perl, particular credit is due to Gary Poster and Benji York,
and their employer, Zope Corporation, for their contributions which
led to ClientForm 0.2 being released.  Thanks also to the many people
who have contributed bug reports.






Download



For installation instructions, see the INSTALL.txt file included in the
distribution. 


Stable release There have been three fairly
minor backwards-incompatible interface changes since version 0.1 (see above), but by default the code operates in a
backwards-compatible mode so that code written for 0.1 should work without
changes.


0.2 includes better support for labels, and a simpler interface (all the old
methods are still there, but some have been deprecated and a few added).








Old release No longer maintained.  I recommend
upgrading from 0.1 to 0.2.


There were many interface changes between 0.0 and 0.1, so you should take
care if upgrading old code from 0.0.


0.1 includes FILE control support for file upload, handling
of disabled list items, and a redesigned interface.







Ancient release No longer maintained.  You
don't want this.







Subversion



The Subversion (SVN) trunk is http://codespeak.net/svn/wwwsearch/ClientForm/trunk, so to check out the source:


svn co http://codespeak.net/svn/wwwsearch/ClientForm/trunk ClientForm






FAQs


    
  
  • Doesn't the standard Python library module, cgi, do this?
  
    No: the cgi module does the server end of the job.  It
     doesn't know how to parse or fill in a form or how to send it back to the
     server.
  
  • Which version of Python do I need?
  
    2.0 or above (ClientForm 0.2; version 0.1 requires Python 1.5.2 or above).
  
  • Is urllib2 required?
  
    No.
  
  • How do I use it without urllib2?
  
    Use .click_request_data() instead of .click().
  
  • Which urllib2 do I need?
  
    You don't.  It's convenient, though.  If you have Python 2.0, you need to
     upgrade to the version from Python 2.1 (available from www.python.org).  Otherwise, you're OK.
  
  • Which license?
  
    ClientForm is dual-licensed: you may pick either the
     BSD license,
     or the ZPL 2.1 (both are
     included in the distribution).
  
  
  • Is XHTML supported?
  
    Yes.  You must pass
     form_parser_class=ClientForm.XHTMLCompatibleFormParser to
     ParseResponse() / ParseFile().  Note this parser
     is less tolerant of bad HTML than the default,
     ClientForm.FormParser
  
  • How do I figure out what control names and values to use?
  
    print form is usually all you need.
     In your code, things like the HTMLForm.items attribute of
     HTMLForm instances can be useful to inspect forms at
     runtime.  Note that it's possible to use item labels instead of item
     names, which can be useful — use the by_label
     arguments to the various methods, and the .get_value_by_label() /
     .set_value_by_label() methods on ListControl.
  
  • What do those '*' characters mean in the string
     representations of list controls?
  
    A * next to an item means that item is selected.
  
  • What do those parentheses (round brackets) mean in the string
     representations of list controls?
  
    Parentheses (foo) around an item mean that item is disabled.
  
  • Why doesn't <some control> turn up in the data returned by
     .click*() when that control has non-None value?
  
    Either the control is disabled, or it is not successful for some other
     reason.  'Successful' (see HTML 4 specification) means that the control
     will cause data to get sent to the server.
  
  • Why does ClientForm not follow the HTML 4.0 / RFC 1866 standards for
     RADIO and multiple-selection SELECT controls?
  
    Because by default, it follows browser behaviour when setting the
     initially-selected items in list controls that have no items explicitly
     selected in the HTML. Use the select_default argument to
     ParseResponse if you want to follow the RFC 1866 rules
     instead.  Note that browser behaviour violates the HTML 4.01 specification
     in the case of RADIO controls.
  
  • Why does .click()ing on a button not work for me?
    
      
    
    • Clicking on a RESET button doesn't do anything, by design
        - this is a library for web automation, not an interactive browser.
        Even in an interactive browser, clicking on RESET sends
        nothing to the server, so there is little point in having
        .click() do anything special here.
    
    • Clicking on a BUTTON TYPE=BUTTON doesn't do anything
        either, also by design.  This time, the reason is that that
        BUTTON is only in the HTML standard so that one can attach
        callbacks to its events.  The callbacks are functions in
        SCRIPT elements (such as Javascript) embedded in the HTML,
        and their execution may result in information getting sent back to the
        server.  ClientForm, however, knows nothing about these callbacks, so
        it can't do anything useful with a click on a BUTTON whose
        type is BUTTON.
    
    • Generally, embedded script may be messing things up in all kinds of
        ways.  See the answer to the next question.
    
    
  
  • Embedded script is messing up my form filling.  What do I do?
  
    See the General FAQs page and the
     next FAQ entry for what to do about this.

  
  • How do I change INPUT TYPE=HIDDEN field values (for example,
      to emulate the effect of JavaScript code)?
  
    As with any control, set the control's readonly attribute
     false.

    form.find_control("foo").readonly = False  # allow changing .value of control foo
form.set_all_readonly(False)  # allow changing the .value of all controls
    

  
    • 
  
  • I'm having trouble debugging my code.
  
    The ClientCookie package makes it
     easy to get .seek()able response objects, which is
     convenient for debugging.  See also here for few
     relevant tips.  Also see  General
     FAQs.
  
  • I have a control containing a list of integers.  How do I select the one
     whose value is nearest to the one I want?

    import bisect
def closest_int_value(form, ctrl_name, value):
    values = map(int, [item.name for item in form.find_control(ctrl_name).items])
    return str(values[bisect.bisect(values, value) - 1])

form["distance"] = [closest_int_value(form, "distance", 23)]
    

  
    • 
  
  • Where can I find out more about the HTML and HTTP standards?
  




I prefer questions and comments to be sent to the 
mailing list rather than direct to me.


John J. Lee,
July 2008.

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