Python Web Tutorial

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Python Web Tutorial

  1. 1. Rob
Sanderson
 
‐
azaroth42@gmail.com
 
‐
@azaroth42
 Ed
Summers
 
‐
ehs@pobox.com
 
‐
@edsu
 http://www.flickr.com/photos/42311564@N00/2355590274/ Dojo: Python for Web Interaction Rob Sanderson, Ed Summers Dev8D, Feb 24-27 2010, London
  2. 2. Overview Python Dojo •  Python Introduction •  Web Programming Kata: •  Find bands on Wikipedia •  Find nationality of band •  Find population of nation •  Create chart of bands normalized by population Dojo: Python for Web Interaction Rob Sanderson, Ed Summers Dev8D, Feb 24-27 2010, London
  3. 3. Python: Data Types >>> ‘string’ “string” # strings are immutable >>> u’unicode: xe4‘ # ä >>> “””string that can have multiple lines””” >>> 1 # int >>> 1L # long int >>> 1.0 # float >>> [list, of, items] # mutable >>> (tuple, of, items) # immutable >>> {key : value, key2 : value2, …} >>> None >>> True, False # booleans Dojo: Python for Web Interaction Rob Sanderson, Ed Summers Dev8D, Feb 24-27 2010, London
  4. 4. Python: Flow Control >>> for x in iterable: ... # process x >>> if test or test2 and not test3: ... # do something ... elif test4: ... # do something else ... else: ... # otherwise do this >>> while test: ... # do something >>> try: ... # try something ... except ExceptionType: ... # recover Dojo: Python for Web Interaction Rob Sanderson, Ed Summers Dev8D, Feb 24-27 2010, London
  5. 5. Python: Classes, Functions >>> def functionName(arg1, arg2=default): ... # do something >>> class ClassName (ParentClass): ... property = value ... ... def __init__(self): ... # initialize ... ... def method(self, arg1, arg2=default): ... # do something >>> what = ClassName() >>> what.method(“arg1”, arg2=“arg2”) Dojo: Python for Web Interaction Rob Sanderson, Ed Summers Dev8D, Feb 24-27 2010, London
  6. 6. Python: Other Important Stuff >>> break >>> continue >>> raise Exception >>> return value >>> pass # no operation >>> import module >>> from module import something >>> from module import * # import everything Dojo: Python for Web Interaction Rob Sanderson, Ed Summers Dev8D, Feb 24-27 2010, London
  7. 7. Python Master Class: Basics >>> ‘abcd’[0] = ‘z’ # error, as strings are immutable >>> ‘’.join([list of strings]) # create string from list >>> var = [x for x in iterable] # list comprehension >>> a, b, c = (“a”, “b”, “c”) # scattered assignment >>> var = a if test else b # ternary operator (test ? a : b) >>> anonFn = lambda x: x+1 # anonFn(1)  2 >>> var = Function # var()  run Function >>> var = Class # var()  new instance of Class Dojo: Python for Web Interaction Rob Sanderson, Ed Summers Dev8D, Feb 24-27 2010, London
  8. 8. Python Master Class: Iterators class Reverse: "Iterator for looping over a sequence backwards" def __init__(self, data): self.data = data self.index = len(data) def __iter__(self): return self def next(self): if self.index == 0: raise StopIteration self.index = self.index - 1 return self.data[self.index] >>> for char in Reverse('spam'): ... print char m a p s Dojo: Python for Web Interaction Rob Sanderson, Ed Summers Dev8D, Feb 24-27 2010, London
  9. 9. Python Master Class: Generators def reverse(data): for index in range(len(data)-1, -1, -1): yield data[index] >>> for char in reverse('golf'): ... print char ... f l o g Dojo: Python for Web Interaction Rob Sanderson, Ed Summers Dev8D, Feb 24-27 2010, London
  10. 10. urllib >>> import urllib >>> urllib.quote('~azaroth/s?q=http://foo.com/') '%7Eazaroth/s%3Fq%3Dhttp%3A//foo.com/' >>> urllib.unquote('%7Eazaroth/s%3Fq%3Dhttp%3A//foo.com/') '~azaroth/s?q=http://foo.com/' >>> fh = urllib.urlopen('http://www.google.com/') >>> html = fh.read() >>> fh.close() >>> fh.getcode() 200 >>> fh.headers.dict['content-type'] 'text/html; charset=ISO-8859-1' Dojo: Python for Web Interaction Rob Sanderson, Ed Summers Dev8D, Feb 24-27 2010, London
  11. 11. urllib2 >>> import urllib2 >>> ph = urllib2.ProxyHandler( {'http' : 'http://proxyout.lanl.gov:8080/'}) >>> opener = urllib2.build_opener(ph) >>> urllib2.install_opener(opener) >>> # From now on, all requests will go through proxy >>> r = urllib2.Request('http://www.google.com/') >>> r.add_header('Referrer', 'http://www.somewhere.net') >>> fh = urllib2.urlopen(r) >>> html = fh.read() >>> fh.close() >>> # fh is the same as urllib's for headers/status Dojo: Python for Web Interaction Rob Sanderson, Ed Summerrs Dev8D, Feb 24-27 2010, London
  12. 12. urlparse >>> import urlparse >>> pr = urlparse.urlparse( 'https://www.google.com/search?q=foo&bar=bz#frag') >>> pr.scheme 'https' >>> pr.hostname 'www.google.com' >>> pr.path '/search' >>> pr.query 'q=foo&bar=bz' >>> pr.fragment 'frag' Dojo: Python for Web Interaction Rob Sanderson, Ed Summers Dev8D, Feb 24-27 2010, London
  13. 13. httplib >>> import httplib >>> cxn = httplib.HTTPConnection('www.google.com') >>> hdrs = {'Accept' : 'application/rdf+xml'} >>> path = "/search?q=some+search+query" >>> cxn.request("HEAD", path, headers=hdrs) >>> resp = cxn.getresponse() >>> resp.status 200 >>> resp_hdrs = dict(resp.getheaders()) >>> resp_hdrs['content-type'] # :( 'text/html; charset=ISO-8859-1' >>> data = resp.read() >>> cxn.close() Dojo: Python for Web Interaction Rob Sanderson, Ed Summers Dev8D, Feb 24-27 2010, London
  14. 14. lxml $ easy_install lxml >>> from lxml import etree >>> et = etree.XML('<a b="B"> A <c>C</c> </a>') >>> et.text ' A ' >>> et.attrib['b'] 'B' >>> for elem in et.iterchildren(): ... print elem <Element c at 16d1ed0> >>> html = etree.parse(StringIO.StringIO("<html><p>hi"), parser=etree.HTMLParser()) >>> html.xpath('/html/body/p') [<Element p at 16e00f0>] Dojo: Python for Web Interaction Rob Sanderson, Ed Summers Dev8D, Feb 24-27 2010, London
  15. 15. rdflib $ easy_install rdflib >>> import rdflib as rdf >>> inp = rdf.URLInputSource( 'http://xmlns.com/foaf/spec/20100101.rdf') >>> inp2 = rdf.StringInputSource("<a> <b> <c> .") >>> graph = rdf.ConjunctiveGraph() >>> graph.parse(inp) >>> sparql = "SELECT ?l WHERE {?w rdfs:label ?l . }" >>> res = graph.query(sparql, initNs={'rdfs':rdf.RDFS.RDFSNS})) >>> res.selected[0] rdf.Literal(u'Given name') >>> nt = graph.serialize(format='nt') Dojo: Python for Web Interaction Rob Sanderson, Ed Summers Dev8D, Feb 24-27 2010, London
  16. 16. json / simplejson >>> try: import simplejson as json ... except ImportError: import json >>> data = {'o' : (True, None, 1.0), "ints" : [1,2,3]} >>> json.dumps(data) '{"o": [true, null, 1.0], "ints": [1, 2, 3]}' >>> json.dumps(data, separators=(',', ':')) # compact '{"o":[true,null,1.0],"ints":[1,2,3]}' >>> json.loads('[1,2,"foo",null]') [1, 2, u'foo', None] Dojo: Python for Web Interaction Rob Sanderson, Ed Summers Dev8D, Feb 24-27 2010, London
  17. 17. mod_python, mod_wsgi import cgitb from mod_python import apache from mod_python.util import FieldStorage def handler(req): try: form = FieldStorage(req) # dict-like object for query path = req.uri req.status = 200 req.content_type = "text/plain" req.send_http_header() req.write(path) except: req.content_type = "text/html" cgitb.Hook(file=req).handle() return apache.OK Dojo: Python for Web Interaction Rob Sanderson, Ed Summers Dev8D, Feb 24-27 2010, London

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