Python 基本语法

l = [1, 2, 3]
print l # [1, 2, 3]

t = tuple(l)
print t # (1, 2, 3)

l1 = list(t)
print l1 #[1, 2, 3]

name = "Peter Zhang"
age = 25
print "Name: %s; Age: %d" % (name, age)
# Name: Peter Zhang; Age: 25

t = (1, 2, 3, 1, 2, 3)

print t.count(2) # 2

t = (1, 2, 3, 1, 2, 3)

print t.index(3) # 2
try:
    print t.index(4)
except ValueError, ve:
    print "there is no 4 in tuple"  # there is no 4 in tuple

d = {}
d["1"] = "one"
d["2"] = "two"
d["3"] = "three"

del d["3"]

for key, value in d.items():
    print "%s --> %s" % (key, value)
#1 --> one
#2 --> two

d1 = {"1":"one", "2":"two"}
d1.clear()

print d1 # {}

d1 = {"1":"one", "2":"two"}
d2 = d1.copy()

print d2 #{‘1‘: ‘one‘, ‘2‘: ‘two‘}

l = [1, 2, 3]
t = (1, 2, 3)

d3 = {}.fromkeys(l)
print d3 #{1: None, 2: None, 3: None}

d4 = {}.fromkeys(t, "default")
print d4 #{1: ‘default‘, 2: ‘default‘, 3: ‘default‘}

d5 = {1:"one", 2:"two", 3:"three"}

print d5.get(1) #one
print d5.get(5) #None
print d5.get(5, "test") #test

d6 = {1:"one", 2:"two", 3:"three"}

print d6.has_key(1)  #True
print d6.has_key(5)  #False

d7 = {1:"one", 2:"two", 3:"three"}

for item in d7.items():
    print item
#(1, ‘one‘)
#(2, ‘two‘)
#(3, ‘three‘)

for key, value in d7.items():
    print "%s -- %s" % (key, value)
#1 -- one
#2 -- two
#3 -- three

d8 = {1:"one", 2:"two", 3:"three"}

for key in d8.keys():
    print key
#1
#2
#3

d8 = {1:"one", 2:"two", 3:"three"}

for value in d8.values():
    print value
#one
#two
#three

d9 = {1:"one", 2:"two", 3:"three"}
print d9.pop(1) #one
print d9 #{2: ‘two‘, 3: ‘three‘}
print d9.pop(5, None) #None
try:
    d9.pop(5)  # raise KeyError
except KeyError, ke:
    print  "KeyError:", ke #KeyError:5

d10 = {1:"one", 2:"two", 3:"three"}

print d10.popitem()  #(1, ‘one‘)
print d10  #{2: ‘two‘, 3: ‘three‘}

d = {1:"one", 2:"two", 3:"three"}

print d.setdefault(1)  #one
print d.setdefault(5)  #None
print d  #{1: ‘one‘, 2: ‘two‘, 3: ‘three‘, 5: None}
print d.setdefault(6, "six") #six
print d  #{1: ‘one‘, 2: ‘two‘, 3: ‘three‘, 5: None, 6: ‘six‘}

d = {1:"one", 2:"two", 3:"three"}
d2 = {1:"first", 4:"forth"}

d.update(d2)
print d  #{1: ‘first‘, 2: ‘two‘, 3: ‘three‘, 4: ‘forth‘}

d = {1:"one", 2:"two", 3:"three"}
for key, value in d.viewitems():
    print "%s - %s" % (key, value)
#1 - one
#2 - two
#3 - three

d = {1:"one", 2:"two", 3:"three"}
for key in d.viewkeys():
    print key
#1
#2
#3

d = {1:"one", 2:"two", 3:"three"}
for value in d.viewvalues():
    print value
#one
#two
#three

 1 numbers = ["zero", "one", "two", "three", "four"]
 2 
 3 print numbers[1] # one
 4 print numbers[-1] # four
 5 #print numbers[5] # raise IndexError
 6 
 7 print numbers[:] # [‘zero‘, ‘one‘, ‘two‘, ‘three‘, ‘four‘]
 8 print numbers[3:] # [‘three‘, ‘four‘]
 9 print numbers[:2] # [‘zero‘, ‘one‘]
10 print numbers[2:4] # [‘two‘, ‘three‘]
11 print numbers[1:-1] # [‘one‘, ‘two‘, ‘three‘] 

class Animal:
    pass #empty block

class Person:
    Count = 0
    def __init__(self, name, age):
        Person.Count += 1
        self.name = name
        self.__age = age

p = Person("peter", 25)
p1 = Person("john", 20)

print Person.Count #2
print p.name #peter
print p.__age #AttributeError: Person instance has no attribute ‘__age‘

 1 class SchoolMember:
 2     ‘‘‘Represent any school member.‘‘‘
 3     def __init__(self, name, age):
 4         self.name = name
 5         self.age = age
 6         print "Initializing a school member."
 7     
 8     def tell(self):
 9         ‘‘‘Tell my details‘‘‘
10         print "Name: %s, Age: %s, " % (self.name, self.age),
11 
12 class Teacher(SchoolMember):
13     ‘‘‘Represent a teacher.‘‘‘
14     def __init__(self, name, age, salary):
15         SchoolMember.__init__(self, name, age)
16         self.salary = salary
17         print "Initializing a teacher"
18 
19     def tell(self):
20         SchoolMember.tell(self)
21         print "Salary: %d" % self.salary
22 
23 class Student(SchoolMember):
24     ‘‘‘Represent a student.‘‘‘
25     def __init__(self, name, age, marks):
26         SchoolMember.__init__(self, name, age)
27         self.marks = marks
28         print "Initializing a student"
29 
30     def tell(self):
31         SchoolMember.tell(self)
32         print "Marks: %d" % self.marks
33 
34 print SchoolMember.__doc__
35 print Teacher.__doc__
36 print Student.__doc__
37 
38 t = Teacher("Mr. Li", 30, 9000)
39 s = Student("Peter", 25, 90)
40 
41 members = [t, s]
42 
43 for m in members:
44     m.tell()

Represent any school member.
Represent a teacher.
Represent a student.
Initializing a school member.
Initializing a teacher
Initializing a school member.
Initializing a student
Name: Mr. Li, Age: 30,  Salary: 9000
Name: Peter, Age: 25,  Marks: 90

 1 test = ‘‘‘ 2 This is a program about file I/O.
 3 
 4 Author: Peter Zhange
 5 Date: 2011/12/25
 6 ‘‘‘
 7 
 8 f = file("test.txt", "w") # open for writing, the file will be created if the file doesn‘t exist
 9 f.write(test) # write text to file
10 f.close() # close the file
11 
12 f = file("test.txt") # if no mode is specified, the default mode is readonly.
13 
14 while True:
15     line = f.readline()
16     if len(line) == 0:  # zero length indicates the EOF of the file
17         break
18     print line,
19 
20 f.close()

import cPickle

datafile = "data.data"

namelist = ["peter", "john", "king"]

f = file(datafile, "w")
cPickle.dump(namelist, f)
f.close()

del namelist

f = file(datafile)
storednamelist = cPickle.load(f)

print storednamelist
#[‘peter‘, ‘john‘, ‘king‘]

try:
    print 1/0
except ZeroDivisionError, e:
    print e
except:
    print "error or exception occurred."

#integer division or modulo by zero

class ShortInputException(Exception):
    ‘‘‘A user-defined exception class‘‘‘
    def __init__(self, length, atleast):
        Exception.__init__(self)
        self.length = length
        self.atleast = atleast

try:
    s = raw_input("enter someting-->")
    if len(s) < 3:
        raise ShortInputException(len(s), 3)
except EOFError:
    print "why you input an EOF?"
except ShortInputException, ex:
    print "The lenght of input is %d, was expecting at the least %d" % (ex.length, ex.atleast)
else:
    print "no exception"
#The lenght of input is 1, was expecting at the least 3

try:
    f = file("test.txt")
    while True:
        line = f.readline()
        if len(line) == 0:
            break
        time.sleep(2)
        print line,
finally:
    f.close()
    print "Cleaning up..."

s = sys.stdin.readline()

sys.stdout.write(s)

class Array:
    __list = []

    def __init__(self):
        print "constructor"

    def __del__(self):
        print "destructor"

    def __str__(self):
        return "this self-defined array class"

    def __getitem__(self, key):
        return self.__list[key]

    def __len__(self):
        return len(self.__list)

    def Add(self, value):
        self.__list.append(value)

    def Remove(self, index):
        del self.__list[index]

    def DisplayItems(self):
        print "show all items----"
        for item in self.__list:
            print item

arr = Array()   #constructor
print arr    #this self-defined array class
print len(arr)   #0
arr.Add(1)
arr.Add(2)
arr.Add(3)
print len(arr)   #3
print arr[0]   #1
arr.DisplayItems()
#show all items----
#1
#2
#3
arr.Remove(1)
arr.DisplayItems()
#show all items----
#1
#3
#destructor

list1 = [1, 2, 3, 4, 5]
list2 = [i*2 for i in list1 if i > 3]

print list1  #[1, 2, 3, 4, 5]
print list2  #[8, 10]

def powersum(power, *args):
    total = 0
    for i in args:
        total += pow(i, power)
    return total

print powersum(2, 1, 2, 3)   #14 

def displaydic(**args):
    for key,value in args.items():
        print "key:%s;value:%s" % (key, value)


displaydic(a="one", b="two", c="three")
#key:a;value:one
#key:c;value:three
#key:b;value:two

func = lambda s: s * 3
print func("peter ")  #peter peter peter

func2 = lambda a, b: a * b
print func2(2, 3)  #6

cmd = "print ‘hello world‘"
exec cmd   #hello world

expression = "10 * 2 + 5"
print eval(expression)    #25

flag = True

assert flag == True

try:
    assert flag == False
except AssertionError, err:
    print "failed"
else:
    print "pass"

arr = [1, 2, 3]
print `arr`    #[1, 2, 3]
print repr(arr)    #[1, 2, 3]