人生苦短我用python python如何快速入门?

>>> help(5)Help on int object:(etc etc)>>> dir(5)['__abs__', '__add__', ...]>>> abs.__doc__'abs(number) -> numberReturn the absolute value of the argument.'

>>> myvar = 3>>> myvar += 2>>> myvar5>>> myvar -= 1>>> myvar4"""This is a multiline comment.The following lines concatenate the two strings.""">>> mystring = "Hello">>> mystring += " world.">>> print mystringHello world.# This swaps the variables in one line(!).# It doesn't violate strong typing because values aren't# actually being assigned, but new objects are bound to# the old names.>>> myvar, mystring = mystring, myvar

>>> sample = [1, ["another", "list"], ("a", "tuple")]>>> mylist = ["List item 1", 2, 3.14]>>> mylist[0] = "List item 1 again" # We're changing the item.>>> mylist[-1] = 3.21 # Here, we refer to the last item.>>> mydict = {"Key 1": "Value 1", 2: 3, "pi": 3.14}>>> mydict["pi"] = 3.15 # This is how you change dictionary values.>>> mytuple = (1, 2, 3)>>> myfunction = len>>> print myfunction(mylist)3

>>> mylist = ["List item 1", 2, 3.14]>>> print mylist[:]['List item 1', 2, 3.1400000000000001]>>> print mylist[0:2]['List item 1', 2]>>> print mylist[-3:-1]['List item 1', 2]>>> print mylist[1:][2, 3.14]# Adding a third parameter, "step" will have Python step in# N item increments, rather than 1.# E.g., this will return the first item, then go to the third and# return that (so, items 0 and 2 in 0-indexing).>>> print mylist[::2]['List item 1', 3.14]

>>>print "Name: %s/Number: %s/String: %s" % (myclass.name, 3, 3 * "-")Name: PoromenosNumber: 3String: ---strString = """This isa multilinestring."""# WARNING: Watch out for the trailing s in "%(key)s".>>> print "This %(verb)s a %(noun)s." % {"noun": "test", "verb": "is"}This is a test.

rangelist = range(10)>>> print rangelist[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]for number in rangelist: # Check if number is one of # the numbers in the tuple. if number in (3, 4, 7, 9):  # "Break" terminates a for without  # executing the "else" clause.  break else:  # "Continue" starts the next iteration  # of the loop. It's rather useless here,  # as it's the last statement of the loop.  continueelse: # The "else" clause is optional and is # executed only if the loop didn't "break". pass # Do nothingif rangelist[1] == 2: print "The second item (lists are 0-based) is 2"elif rangelist[1] == 3: print "The second item (lists are 0-based) is 3"else: print "Dunno"while rangelist[1] == 1: pass

# 作用等同于 def funcvar(x): return x + 1funcvar = lambda x: x + 1>>> print funcvar(1)2# an_int 和 a_string 是可选参数，它们有默认值# 如果调用 passing_example 时只指定一个参数，那么 an_int 缺省为 2 ，a_string 缺省为 A default string。如果调用 passing_example 时指定了前面两个参数，a_string 仍缺省为 A default string。# a_list 是必备参数，因为它没有指定缺省值。def passing_example(a_list, an_int=2, a_string="A default string"): a_list.append("A new item") an_int = 4 return a_list, an_int, a_string>>> my_list = [1, 2, 3]>>> my_int = 10>>> print passing_example(my_list, my_int)([1, 2, 3, 'A new item'], 4, "A default string")>>> my_list[1, 2, 3, 'A new item']>>> my_int10

class MyClass(object): common = 10 def __init__(self):  self.myvariable = 3 def myfunction(self, arg1, arg2):  return self.myvariable # This is the class instantiation>>> classinstance = MyClass()>>> classinstance.myfunction(1, 2)3# This variable is shared by all classes.>>> classinstance2 = MyClass()>>> classinstance.common10>>> classinstance2.common10# Note how we use the class name# instead of the instance.>>> MyClass.common = 30>>> classinstance.common30>>> classinstance2.common30# This will not update the variable on the class,# instead it will bind a new object to the old# variable name.>>> classinstance.common = 10>>> classinstance.common10>>> classinstance2.common30>>> MyClass.common = 50# This has not changed, because "common" is# now an instance variable.>>> classinstance.common10>>> classinstance2.common50# This class inherits from MyClass. The example# class above inherits from "object", which makes# it what's called a "new-style class".# Multiple inheritance is declared as:# class OtherClass(MyClass1, MyClass2, MyClassN)class OtherClass(MyClass): # The "self" argument is passed automatically # and refers to the class instance, so you can set # instance variables as above, but from inside the class. def __init__(self, arg1):  self.myvariable = 3  print arg1>>> classinstance = OtherClass("hello")hello>>> classinstance.myfunction(1, 2)3# This class doesn't have a .test member, but# we can add one to the instance anyway. Note# that this will only be a member of classinstance.>>> classinstance.test = 10>>> classinstance.test10

def some_function(): try:  # Division by zero raises an exception  10 / 0 except ZeroDivisionError:  print "Oops, invalid." else:  # Exception didn't occur, we're good.  pass finally:  # This is executed after the code block is run  # and all exceptions have been handled, even  # if a new exception is raised while handling.  print "We're done with that.">>> some_function()Oops, invalid.We're done with that.

import randomfrom time import clockrandomint = random.randint(1, 100)>>> print randomint64

import picklemylist = ["This", "is", 4, 13327]# Open the file C://binary.dat for writing. The letter r before the# filename string is used to prevent backslash escaping.myfile = open(r"C://binary.dat", "w")pickle.dump(mylist, myfile)myfile.close()myfile = open(r"C://text.txt", "w")myfile.write("This is a sample string")myfile.close()myfile = open(r"C://text.txt")>>> print myfile.read()'This is a sample string'myfile.close()# Open the file for reading.myfile = open(r"C://binary.dat")loadedlist = pickle.load(myfile)myfile.close()>>> print loadedlist['This', 'is', 4, 13327]

>>> lst1 = [1, 2, 3]>>> lst2 = [3, 4, 5]>>> print [x * y for x in lst1 for y in lst2][3, 4, 5, 6, 8, 10, 9, 12, 15]>>> print [x for x in lst1 if 4 > x > 1][2, 3]# Check if an item has a specific property.# "any" returns true if any item in the list is true.>>> any([i % 3 for i in [3, 3, 4, 4, 3]])True# This is because 4 % 3 = 1, and 1 is true, so any()# returns True.# Check how many items have this property.>>> sum(1 for i in [3, 3, 4, 4, 3] if i == 4)2>>> del lst1[0]>>> print lst1[2, 3]>>> del lst1

number = 5def myfunc(): # This will print 5. print numberdef anotherfunc(): # This raises an exception because the variable has not # been bound before printing. Python knows that it an # object will be bound to it later and creates a new, local # object instead of accessing the global one. print number number = 3def yetanotherfunc(): global number # This will correctly change the global. number = 3