Python

Exception

try:
   raise Exception("not allowed")
except ValueError as error:
   print('value error: ' + repr(error))
except SyntaxError as error:
   print('syntax error: ' + repr(error))
else:
    raise Exception("unknown")
try:
   doit()
finally:
   closeIt()

Regular Expression

rexpr = compile(r"([\da-z]+)")
match = rexpr.match(line)
if match != None:
   number = (int) rexpr.group(1)

Datentypen

• List: ['a', 1]; x[1] = 5; x.insert(0, 'firstItem')
• Tupel: ('a', 1), ro

Spezielle Methoden/Attribute

• Statische Methoden:

class X:
   @staticmethod
   def doIt(param):
      pass

X.doIt(True)

• Feststellen, ob Attribut existiert: hasattr(instance, nameOfAttribute)
• dynamischer Code:

exec 'import ' + module

Dictionary

x = { 'key' : 'val', 'xyz': 3 }
x['key'] = value
del x['key'];
contains = 'key' in x and 'key2' not in x
size = len(x)
for pair in x.iteritems():
  key = pair[0]
for key in x.iterkeys():
  print key

• x.itervalues()
• x.setdefault(key[, value]): setzt Wert nur, wenn noch nicht gesetzt
• x.keys(), x.values()
• x.copy(): flache Kopie
• x.update(dict): addiert dict zu x

Mengen

s = set(['y', 3]) ; f = frozenset(['y', 3]) 
for elem in s:
  print elem
size = len(s)
contains = 3 in s and 4 not in s
intersection = s & f
union = s | f
isPartOf = s <= f
diff = s - f

Dateien

with open(self._filename, "r") as fp:
  for line in fp:
     print line
fp.close()

Typcheck

isStringOrSubclass = isinstance(aVariable, str)
isString = type(aVariable) is str
isList = type([1, 2]) is list
isDict = type({ 0:"a", 1:"b" }) is dict

Formatierung

"{:3.7f} {:s} {:07d}".format(3.14, "hello", 100)
"{0:d} / {0:x}".format(714)

Klasse als Sequenz

Damit eine Klasse mit "x in classInstance" angesprochen werden kann, muss es __iter__() und __next__() geben:

class Example:
  def __init__():
    self._nextItems = []
  def __iter__():
    self._nextItems = [1, 2, 3]
    return self
  def __next__():
    if len(self._nextItem) == 0:
      raise StopIteration
    else:
      rc = self._nextItems[0]
      del self._nextItems[0]
      return rc