Twisted, lxml and re package

Twisted is an event-driven networking engine written in Python and licensed under the open source:

• As a platform, Twisted should be focused on integration. Ideally, all functionality will be accessible through all protocols. Failing that, all functionality should be configurable through at least one protocol, with a seamless and consistent user-interface.
• The next phase of development will be focusing strongly on a configuration system which will unify many disparate pieces of the current infrastructure, and allow them to be tacked together by a non-programmer.

Refer:

• http://twistedmatrix.com/documents/current/core/
• http://krondo.com/wp-content/uploads/2009/08/twisted-intro.html

The event loop at the core of your program.

• reactor basics: http://twistedmatrix.com/documents/current/core/howto/reactor-basics.html
• reactor core: https://twistedmatrix.com/documents/14.0.0/api/twisted.internet.interfaces.IReactorCore.html

Som basic functions in core reactor twisted/internet/base.py:

• class reactor init

  class ReactorBase(object):
      def __init__(self):
          self.threadCallQueue = []
          self._eventTriggers = {}
          self._pendingTimedCalls = []
          self._newTimedCalls = []
          self._cancellations = 0
          self.running = False
          self._started = False
          self._justStopped = False
          self._startedBefore = False
          # reactor internal readers, e.g. the waker.
          self._internalReaders = set()
          self.waker = None
   
          # Arrange for the running attribute to change to True at the right time
          # and let a subclass possibly do other things at that time (eg install
          # signal handlers).
          self.addSystemEventTrigger(
              'during', 'startup', self._reallyStartRunning)
          self.addSystemEventTrigger('during', 'shutdown', self.crash)
          self.addSystemEventTrigger('during', 'shutdown', self.disconnectAll)
   
          if platform.supportsThreads():
              self._initThreads()
          self.installWaker()

• class reactor run: Fire 'startup' System Events, move the reactor to the 'running' state, then run the main loop until it is stopped with stop() or crash()

  @implementer(IReactorCore, IReactorTime, IReactorPluggableResolver)
  class ReactorBase(object):
      def fireSystemEvent(self, eventType):
          """See twisted.internet.interfaces.IReactorCore.fireSystemEvent.
          """
          event = self._eventTriggers.get(eventType)
          if event is not None:
              event.fireEvent()                
      def startRunning(self):
          if self._started:
              raise error.ReactorAlreadyRunning()
          if self._startedBefore:
              raise error.ReactorNotRestartable()
          self._started = True
          self._stopped = False
          if self._registerAsIOThread:
              threadable.registerAsIOThread()
          self.fireSystemEvent('startup')
   
  class _SignalReactorMixin(object):        
      def run(self, installSignalHandlers=True):
          self.startRunning(installSignalHandlers=installSignalHandlers)
          self.mainLoop()
   
      def mainLoop(self):
          while self._started:
              try:
                  while self._started:
                      # Advance simulation time in delayed event
                      # processors.
                      self.runUntilCurrent()
                      t2 = self.timeout()
                      t = self.running and t2
                      self.doIteration(t)
              except:
                  log.msg("Unexpected error in main loop.")
                  log.err()
              else:
                  log.msg('Main loop terminated.')    
      def runUntilCurrent(self):
          """Run all pending timed calls.
          """
          if self.threadCallQueue:
              # Keep track of how many calls we actually make, as we're
              # making them, in case another call is added to the queue
              # while we're in this loop.
              count = 0
              total = len(self.threadCallQueue)
              for (f, a, kw) in self.threadCallQueue:
                  try:
                      f(*a, **kw)
                  except:
                      log.err()
                  count += 1
                  if count == total:
                      break
              del self.threadCallQueue[:count]
              if self.threadCallQueue:
                  self.wakeUp()
   
          # insert new delayed calls now
          self._insertNewDelayedCalls()
   
          now = self.seconds()
          while self._pendingTimedCalls and (self._pendingTimedCalls[0].time <= now):
              call = heappop(self._pendingTimedCalls)
              if call.cancelled:
                  self._cancellations-=1
                  continue
   
              if call.delayed_time > 0:
                  call.activate_delay()
                  heappush(self._pendingTimedCalls, call)
                  continue
   
              try:
                  call.called = 1
                  call.func(*call.args, **call.kw)
              except:
                  log.deferr()
                  if hasattr(call, "creator"):
                      e = "\n"
                      e += " C: previous exception occurred in " + \
                           "a DelayedCall created here:\n"
                      e += " C:"
                      e += "".join(call.creator).rstrip().replace("\n","\n C:")
                      e += "\n"
                      log.msg(e)
   
   
          if (self._cancellations > 50 and
               self._cancellations > len(self._pendingTimedCalls) >> 1):
              self._cancellations = 0
              self._pendingTimedCalls = [x for x in self._pendingTimedCalls
                                         if not x.cancelled]
              heapify(self._pendingTimedCalls)
   
          if self._justStopped:
              self._justStopped = False
              self.fireSystemEvent("shutdown")                        

• class reactor callLater

      def callLater(self, _seconds, _f, *args, **kw):
          """See twisted.internet.interfaces.IReactorTime.callLater.
          """
          assert callable(_f), "%s is not callable" % _f
          assert _seconds >= 0, \
                 "%s is not greater than or equal to 0 seconds" % (_seconds,)
          tple = DelayedCall(self.seconds() + _seconds, _f, args, kw,
                             self._cancelCallLater,
                             self._moveCallLaterSooner,
                             seconds=self.seconds)
          self._newTimedCalls.append(tple)
          return tple

Timeouts, repeated events, and more: when you want things to happen later.

• Sheduling API:
  • https://twistedmatrix.com/documents/14.0.0/api/twisted.internet.task.html
  • https://twistedmatrix.com/documents/14.0.0/api/twisted.internet.interfaces.IReactorTime.html
• example codes: http://twistedmatrix.com/documents/current/core/howto/time.html

Like callback functions, only a lot better.Twisted’s preferred mechanism for controlling the flow of asynchronous code. We would still need a way of saying “do this only when that has finished”.

• introduce defer: http://twistedmatrix.com/documents/current/core/howto/defer-intro.html
• defer API:
  • https://twistedmatrix.com/documents/14.0.0/api/twisted.internet.defer.html
  • https://twistedmatrix.com/documents/14.0.0/api/twisted.internet.defer.Deferred.html
• example codes: http://twistedmatrix.com/documents/current/core/howto/defer.html

Below are some basic function of defer API:

• defer.py: maybeDeferred

  def succeed(result):
      d = Deferred()
      d.callback(result)
      return d
  def fail(result=None):
      d = Deferred()
      d.errback(result)
      return d
  def maybeDeferred(f, *args, **kw):
      try:
          result = f(*args, **kw)
      except:
          return fail(failure.Failure(captureVars=Deferred.debug))
   
      if isinstance(result, Deferred):
          return result
      elif isinstance(result, failure.Failure):
          return fail(result)
      else:
          return succeed(result)

• class Defered:addCallback,callback

      def __init__(self, canceller=None):
          self.callbacks = []
          self._canceller = canceller
          if self.debug:
              self._debugInfo = DebugInfo()
              self._debugInfo.creator = traceback.format_stack()[:-1]
   
      def addCallbacks(self, callback, errback=None,
                       callbackArgs=None, callbackKeywords=None,
                       errbackArgs=None, errbackKeywords=None):
          assert callable(callback)
          assert errback == None or callable(errback)
          cbs = ((callback, callbackArgs, callbackKeywords),
                 (errback or (passthru), errbackArgs, errbackKeywords))
          self.callbacks.append(cbs)
   
          if self.called:
              self._runCallbacks()
          return self
      def addCallback(self, callback, *args, **kw):
          return self.addCallbacks(callback, callbackArgs=args,
                                   callbackKeywords=kw)
      def addErrback(self, errback, *args, **kw):
          return self.addCallbacks(passthru, errback,
                                   errbackArgs=args,
                                   errbackKeywords=kw)
      def callback(self, result):
          assert not isinstance(result, Deferred)
          self._startRunCallbacks(result)                                 

• class Defered: inlineCallbacks(f): helps you write Deferred-using code that looks like a regular sequential function.

TCP servers , TCP clients , UDP networking and Using processes

• Threads API: https://twistedmatrix.com/documents/14.0.0/api/twisted.internet.interfaces.IReactorThreads.html
• example codes: http://twistedmatrix.com/documents/current/core/howto/threading.html

The lxml XML toolkit is a Pythonic binding for the C libraries libxml2 and libxslt:

• http://lxml.de/index.html
• http://lxml.de/api/index.html
• https://docs.python.org/2/library/xml.etree.elementtree.html

two the most basic classes in lxml packages for parsing xml and html:

• ElementTree:https://docs.python.org/2/library/xml.etree.elementtree.html#elementtree-objects
• HTMLElement:https://docs.python.org/2/library/xml.etree.elementtree.html#element-objects

refer: http://lxml.de/parsing.html
etree.parse return lxml.etree._ElementTree object

• Parsing XML
  • XML String

    import StringIO
    from lxml import etree
    f = StringIO.StringIO('<foo><bar></bar></foo>')
    tree = etree.parse(f)

  • XML file

    from lxml import etree
     
    tree = etree.parse("doc/test.xml")

  • Iterate Parsing xml

    import StringIO
    from lxml import etree
    f = StringIO.StringIO('<foo><bar></bar></foo>')    
    context = etree.iterparse(f)
    for action, elem in context:
        print("%s: %s" % (action, elem.tag))

    end: bar
    end: foo

• Parsing HTML
  • HTML String

    import StringIO
    from lxml import etree
    from lxml.html import HTMLParser
     
    broken_html = "<html><head><title>test<body><h1>page title</h3>"
    parser = HTMLParser()
    tree   = etree.parse(StringIO.StringIO(broken_html), parser)
    result = etree.tostring(tree.getroot(), pretty_print=True, method="html")
    print(result)

  • HTML file

    from lxml import etree
    from lxml.html import HTMLParser
     
    parser = HTMLParser()
    tree   = etree.parse('index.html', parser)

  • Iterate Parsing HTML

    import StringIO
    from lxml import etree
     
    with open('index.html', 'r') as f:
        htmlcontent = f.read()
        context = etree.iterparse(StringIO.StringIO(htmlcontent), html = True)
        for action, elem in context:
            print("%s: %s" % (action, elem.tag))

XPath for python:

• https://docs.python.org/2/library/xml.etree.elementtree.html#elementtree-xpath
• http://lxml.de/xpathxslt.html

refer: http://www.w3schools.com/XPath/xpath_syntax.asp

XPath Expressions:

• Selecting Nodes
• Predicates: Predicates are used to find a specific node or a node that contains a specific value
• Selecting Unknown Nodes
• Selecting Several Paths

XPath function return:

• XPath() function return value are array of HTMLElement objects
• If you add string option in XPath function //text(), XPath will return value are array of String Objects

• Simple Example for xml

  import StringIO
  from lxml import etree
  f = StringIO.StringIO('<foo><bar></bar></foo>')
  tree = etree.parse(f)
  r = tree.xpath('/foo/bar')
  print r[0].tag
  len(r)
  r = tree.xpath('bar')
  r[0].tag
  print r[0].tag

  ⇒output:

  bar
  bar

• xpath with html
  • Information of tag which you want parser:

    <div title="buyer-name">Carson Busses</div>
    <span class="item-price">$29.95</span>

  • code parser

    from lxml import html
    import requests
     
    page = requests.get('http://econpy.pythonanywhere.com/ex/001.html')
    tree = html.fromstring(page.text)
    #This will create a list of buyers:
    buyers = tree.xpath('//div[@title="buyer-name"]/text()')
    #This will create a list of prices
    prices = tree.xpath('//span[@class="item-price"]/text()')
     
    print 'Buyers: ', buyers
    print 'Prices: ', prices

    ⇒output:

    Buyers:  ['Carson Busses', 'Earl E. Byrd', 'Patty Cakes', 'Derri Anne Connecticut', 'Moe Dess', 'Leda Doggslife', 'Dan Druff', 'Al Fresco', 'Ido Hoe', 'Howie Kisses', 'nt', 'Ben D. Rules', 'Ave Sectomy', 'Gary Shattire', 'Bobbi Soks', 'Sheila Takya', 'Rose Tattoo', 'Moe Tell']
    Prices:  ['$29.95', '$8.37', '$15.26', '$19.25', '$19.25', '$13.99', '$31.57', '$8.49', '$14.47', '$15.86', '$11.11', '$15.98', '$16.27', '$7.50', '$50.85', '$14.26', '
    0.09']

• parser element with basic HTMLParser

  from HTMLParser import HTMLParser
   
  # create a subclass and override the handler methods
  class MyHTMLParser(HTMLParser):
      def handle_starttag(self, tag, attrs):
          print "Encountered a start tag:", tag
      def handle_endtag(self, tag):
          print "Encountered an end tag :", tag
      def handle_data(self, data):
          print "Encountered some data  :", data
   
  # instantiate the parser and fed it some HTML
  parser = MyHTMLParser()
  parser.feed('''<html><head><title>Test</title></head>
              <body><h1>Parse me!</h1></body></html>''')

  output:

  Encountered a start tag: html
  Encountered a start tag: head
  Encountered a start tag: title
  Encountered some data  : Test
  Encountered an end tag : title
  Encountered an end tag : head
  Encountered some data  :
  
  Encountered a start tag: body
  Encountered a start tag: h1
  Encountered some data  : Parse me!
  Encountered an end tag : h1
  Encountered an end tag : body
  Encountered an end tag : html

refer: http://lxml.de/lxmlhtml.html

• parse html from request:

  from lxml import html, etree
  from lxml.html import HTMLParser
  import StringIO
  import requests
   
  tree = html.parse('http://www.google.com')
  tree.write('index.html')

  Or

  from lxml import html
  import requests
   
  page = requests.get('http://www.google.com')
  tree = html.fromstring(page.text)
  r = tree.xpath('//title');
  print r[0].text

• parse html from local file

  from lxml import html as HTML
   
  tree = HTML.parse('index.html')
  r = tree.xpath('//title');
  print r[0].tag
  print r[0].text

• parser html with HTMLParser:

  import StringIO
  from lxml import etree
  from lxml.html import HTMLParser
   
  broken_html = "<html><head><title>test<body><h1>page title</h3>"
  parser = HTMLParser()
  tree   = etree.parse(StringIO.StringIO(broken_html), parser)
  result = etree.tostring(tree.getroot(), pretty_print=True, method="html")
  print(result)

• Build xml using xml.etree.ElementTree:

  from xml.etree import ElementTree as ET
  '''
  <?xml version="1.0"?>
  <data>
      <country name="Liechtenstein">
          <rank>1</rank>
          <year>2008</year>
      </country>
      <country name="Singapore">
          <rank>4</rank>
          <year>2011</year>
      </country>
  </data>
  '''
  data = ET.Element('data')
   
  country1 = ET.SubElement(data, 'country', {'name':'Liechtenstein'})
  rank1 = ET.SubElement(country1, 'rank')
  rank1.text = '1'
  year1 = ET.SubElement(country1, 'year')
  year1.text = '2008'
   
  country2 = ET.SubElement(data, 'country', {'name':'Singapore'})
  rank2 = ET.SubElement(country2, 'rank')
  rank2.text = '4'
  year2 = ET.SubElement(country2, 'year')
  year2.text = '2011'
  print ET.tostring(data)

  output:

  <data><country name="Liechtenstein"><rank>1</rank><year>2008</year></country><country name="Singapore"><rank>4</rank><year>2011</year></country></data>

• Build xml using lxml.etree:

  from lxml import etree as ET
  '''
  <?xml version="1.0"?>
  <data>
      <country name="Liechtenstein">
          <rank>1</rank>
          <year>2008</year>
      </country>
      <country name="Singapore">
          <rank>4</rank>
          <year>2011</year>
      </country>
  </data>
  '''
  data = ET.Element('data')
   
  country1 = ET.SubElement(data, 'country', {'name':'Liechtenstein'})
  rank1 = ET.SubElement(country1, 'rank')
  rank1.text = '1'
  year1 = ET.SubElement(country1, 'year')
  year1.text = '2008'
   
  country2 = ET.SubElement(data, 'country', {'name':'Singapore'})
  rank2 = ET.SubElement(country2, 'rank')
  rank2.text = '4'
  year2 = ET.SubElement(country2, 'year')
  year2.text = '2011'
  print ET.tostring(data)

  output:

  <data><country name="Liechtenstein"><rank>1</rank><year>2008</year></country><country name="Singapore"><rank>4</rank><year>2011</year></country></data>

• Load html from local file

  from lxml.html import HtmlElement
  from lxml import etree
  from lxml import html as HTML
   
  tree = HTML.parse('index.html')
  r = tree.xpath('//div[@id="content"]');
  print(etree.tostring(r[0], pretty_print=True, encoding='utf-8'))

• Print HTMLElement

  from lxml.html import HtmlElement
  from lxml import etree
  from lxml import html as HTML
   
  tree = HTML.parse('index.html')
  r = tree.xpath('//div[@id="content"]');
  print(etree.tostring(r[0], pretty_print=True, method="html"))

• Write html from tree

  from lxml import html, etree
  from lxml.html import HTMLParser
  import StringIO
  import requests
   
  page = requests.get('http://shop.babies.vn')
  parser = HTMLParser()
  tree   = etree.parse(StringIO.StringIO(page.text), parser)
  tree.write('index.html', method = 'html')

  Or

  from lxml import html, etree
  from lxml.html import HTMLParser
  import StringIO
  import requests
   
  tree = html.parse('http://shop.babies.vn')
  tree.write('index.html', method = 'html')

To use re package, we need to import it:

import re

A regular expression (abbreviated regex or regexp) is a sequence of characters that forms a search pattern
refer:

• http://msdn.microsoft.com/en-us/library/az24scfc(v=vs.110).aspx
• python: https://docs.python.org/2/library/re.html#regular-expression-syntax

Match Character

• Character Escapes: The backslash character (\) in a regular expression indicates that the character that follows it either is a special character (as shown in the following table), or should be interpreted literally
  • \t Match a tab: pattern (\w+)\t match “item1\t”, “item2\t” in “item1\titem2\t”
  • \n Match a new line
  • \d Matches any decimal digit
  • \D Matches any character other than a decimal digit.
• Character Classes: A character class matches any one of a set of characters.
  • [character_group] Matches any single character in character_group:pattern [ae] match “a” in “gray” and “a”, “e” in “lane”
  • [^character_group] Negation: Matches any single character that is not in character_group
  • [first-last] Character range: Matches any single character in the range from first to last.
  • \w Matches any word character
  • \W Matches any non-word character.
  • \s Matches any white-space character: Pattern \w\s match “D “ in “ID A1.3”

Anchors: cause a match to succeed or fail depending on the current position in the string

• ^ The match must start at the beginning of the string or line: pattern ^\d{3} match “901” in “901-333-“
• $ The match must occur at the end of the string or before \n at the end of the line or string: pattern -\d{3}$ match ”-333” in ”-901-333”
• \A The match must occur at the start of the string: pattern \A\d{3} match “901” in “901-333-“
• \Z The match must occur at the end of the string or before \n at the end of the string: pattern -\d{3}\Z match ”-333” in “-901-333”

Grouping constructs: Grouping constructs delineate subexpressions of a regular expression and typically capture substrings of an input string

• (subexpression) Captures the matched subexpression and assigns it a one-based ordinal number: pattern (\w)\1 match “ee” in “deep”

Quantifier: A quantifier specifies how many instances of the previous element (which can be a character, a group, or a character class) must be present in the input string for a match to occur

• * Matches the previous element zero or more times: pattern \d*\.\d match “.0”, “19.9”, “219.9”
• + Matches the previous element one or more times: pattern “be+” match “bee” in “been”, “be” in “bent”
• ? Matches the previous element zero or one time: pattern “rai?n” match “ran”, “rain”
• {n} Matches the previous element exactly n times:pattern “,\d{3}“ match ”,043” in “1,043.6”, “,876”, “,543”, and “,210” in “9,876,543,210”
• {n ,} Matches the previous element at least n times: pattern “\d{2,}“ match “166”, “29”, “1930”
• {n,m} Matches the previous element at least n times, but no more than m times: pattern “\d{3,5}“ match “166”, “17668” “19302” in “193024”

refer: http://www.pythonforbeginners.com/regex/regular-expressions-in-python

re Flags:

# flags
I = IGNORECASE = sre_compile.SRE_FLAG_IGNORECASE # ignore case
L = LOCALE = sre_compile.SRE_FLAG_LOCALE # assume current 8-bit locale
U = UNICODE = sre_compile.SRE_FLAG_UNICODE # assume unicode locale
M = MULTILINE = sre_compile.SRE_FLAG_MULTILINE # make anchors look for newline
S = DOTALL = sre_compile.SRE_FLAG_DOTALL # make dot match newline
X = VERBOSE = sre_compile.SRE_FLAG_VERBOSE # ignore whitespace and comments

findall: The findall() is probably the single most powerful function in the re module

1. Example 1:

   str = 'purple alice@google.com, blah monkey bob@abc.com blah dishwasher'
    
   ## Here re.findall() returns a list of all the found email strings
   emails = re.findall(r'[\w\.-]+@[\w\.-]+', str) ## ['alice@google.com', 'bob@abc.com']
    
   for email in emails:
       # do something with each found email string
       print email

   Understand pattern syntax above:

• [\w\.-]+ ⇒ Begin with one or multiple(sign: +) in group(sign: []): word(sign: \w) or character .(sign: \.) or character -
• @[\w\.-]+ ⇒ next of it is character @ and one or multiple characters in group: [word, . , -]

1. Example 2:

   # Open file
   f = open('test.txt', 'r')
    
   # Feed the file text into findall(); it returns a list of all the found strings
   strings = re.findall(r'some pattern', f.read())

• re.search: The re.search() method takes a regular expression pattern and a string and searches for that pattern within the string

  str = 'an example word:cat!!'
  match = re.search(r'word:www', str)
  # If-statement after search() tests if it succeeded
    if match:                      
      print 'found', match.group() ## 'found word:cat'
    else:
      print 'did not find'

  As you can see in the example below, I have used the | operator, which search for either pattern I specify.

  import re
  programming = ["Python", "Perl", "PHP", "C++"]
  pat = "^B|^P|i$|H$"
  for lang in programming:
      if re.search(pat,lang,re.IGNORECASE):
          print lang , "FOUND"
      else:
          print lang, "NOT FOUND"

  The output of above script will be:

  Python FOUND
  Perl FOUND
  PHP FOUND
  C++ NOT FOUND

• re.search and re.match

  import re
   
  text = "The Attila the Hun Show"
   
  # a single character
  m = re.match(".", text)
  if m: print repr("."), "=>", repr(m.group(0))
   
  # any string of characters
  m = re.match(".*", text)
  if m: print repr(".*"), "=>", repr(m.group(0))
   
  # a string of letters (at least one)
  m = re.match("\w+", text)
  if m: print repr("\w+"), "=>", repr(m.group(0))
   
  # a string of digits
  m = re.match("\d+", text)
  if m: print repr("\d+"), "=>", repr(m.group(0))

  output:

  '.' => 'T'
  '.*' => 'The Attila the Hun Show'
  '\\w+' => 'The'

• re.search and re.match:

  import re
   
  print '**********************************'
  text ="10/15/99"
   
  print "match1:"
  m = re.match("(\d{2})/(\d{2})/(\d{2,4})", text)
  if m:
      print m.group(1, 2, 3)
   
  print "search1:"
  s = re.search("(\d{2})/(\d{2})/(\d{2,4})", text)
  if s:
      print s.group(1, 2, 3)    
   
  print '**********************************'
  text ="hello 10/15/99"
  print "match2:"
  m = re.match("(\d{2})/(\d{2})/(\d{2,4})", text)
  if m:
      print m.group(1, 2, 3)
   
  print "search2:"
  s = re.search("(\d{2})/(\d{2})/(\d{2,4})", text)
  if s:
      print s.group(1, 2, 3)

  output:

  **********************************
  match1:
  ('10', '15', '99')
  search1:
  ('10', '15', '99')
  **********************************
  match2:
  search2:
  ('10', '15', '99')

• re.sub: The re.sub() function in the re module can be used to replace substrings
  • first example

    import re
    text = "Python for beginner is a very cool website"
    text2 = re.sub("cool", "good", text)
    print text2

    output

    Python for beginner is a very good website

  • Here is another example (taken from Googles Python class ) which searches for all the email addresses, and changes them to keep the user (1) but have yo-yo-dyne.com as the host.

    str = 'purple alice@google.com, blah monkey bob@abc.com blah dishwasher' 
     
    ## re.sub(pat, replacement, str) -- returns new string with all replacements,
     
    ## 1 is group(1), 2 group(2) in the replacement
     
    print re.sub(r'([\w.-]+)@([\w.-]+)', r'1@yo-yo-dyne.com', str)
    ## purple alice@yo-yo-dyne.com, blah monkey bob@yo-yo-dyne.com blah dishwasher

    output:

    purple alice@yo-yo-dyne.com, blah monkey bob@yo-yo-dyne.com blah dishwasher

• re.compile: With the re.compile() function we can compile pattern into pattern objects, which have methods for various operations such as searching for pattern matches or performing string substitutions.
  • The first example checks if the input from the user contains only letters, spaces or . (no digits) Any other character is not allowed.

    import re
     
    name_check = re.compile(r"[^A-Za-zs.]")
    name = raw_input ("Please, enter your name: ")
    while name_check.search(name):
        print "Please enter your name correctly!"
        name = raw_input ("Please, enter your name: ")

  • The second example checks if the input from the user contains only numbers, parentheses, spaces or hyphen (no letters) Any other character is not allowed

    import re
     
    phone_check = re.compile(r"[^0-9s-()]")
    phone = raw_input ("Please, enter your phone: ")
    while phone_check.search(phone):
        print "Please enter your phone correctly!"
        phone = raw_input ("Please, enter your phone: ")

    The output of above script will be:

    Please, enter your phone: s
    Please enter your phone correctly!

    It will continue to ask until you put in numbers only.