Friday, June 3, 2016

Python Mechanize Cheat Sheet


A very useful python module for navigating through web forms is Mechanize.
In a previous post I wrote about "Browsing in Python with Mechanize".
Today I found this excellent cheat sheet on scraperwiki that I would like to share.
Create a browser object and give it some optional settings.
import mechanize
br = mechanize.Browser()
br.set_all_readonly(False) # allow everything to be written to
br.set_handle_robots(False) # ignore robots
br.set_handle_refresh(False) # can sometimes hang without this
br.addheaders = # [('User-agent', 'Firefox')]
Open a webpage and inspect its contents
response = br.open(url)
print response.read() # the text of the page
response1 = br.response() # get the response again
print response1.read() # can apply lxml.html.fromstring()
Using formsList the forms that are in the page
for form in br.forms():
  print "Form name:", form.name
  print form
To go on the mechanize browser object must have a form selected
br.select_form("form1") # works when form has a name
br.form = list(br.forms())[0] # use when form is unnamed
Using Controls
Iterate through the controls in the form.
for control in br.form.controls:
  print control
  print "type=%s, name=%s value=%s" % (control.type, control.name,br[control.name])
Controls can be found by name
control = br.form.find_control("controlname")
Having a select control tells you what values can be selected
if control.type == "select": # means it's class ClientForm.SelectControl
  for item in control.items:
    print " name=%s values=%s" % (item.name, str([label.text for label in item.get_labels()]))
Because 'Select' type controls can have multiple selections, they must be set with a list, even if it is one element.
print control.value
print control # selected value is starred
control.value = ["ItemName"]
print controlbr[control.name] = ["ItemName"] # equivalent and more normal
Text controls can be set as a string
if control.type == "text": # means it's class ClientForm.TextControl
  control.value = "stuff here"
br["controlname"] = "stuff here" # equivalent
Controls can be set to readonly and disabled.
control.readonly = False
control.disabled = True
OR disable all of them like so
for control in br.form.controls:
 if control.type == "submit": control.disabled = True
Submit the formWhen your form is complete you can submit
response = br.submit()
print response.read()
br.back() # go back
Finding LinksFollowing links in mechanize is a hassle because you need the have the link object.
Sometimes it is easier to get them all and find the link you want from the text.

for link in br.links():
 print link.text, link.url
Follow link and click links is the same as submit and click
request = br.click_link(link)
response = br.follow_link(link)
print response.geturl()
I hope that you got more understanding of the Mechanize module in Python.

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