简明Pyhton教程余下基础内容

类

 

#coding=utf-8
class Person:
    '''Represents a person.'''
    population = 0

    def __init__(self,name):#相当于类的构造函数
        '''Initiatizes the person's date.'''
        self.name = name
        print '(Initializing %s)' % self.name
        Person.population += 1

    def __del__(self):#相当于类的析构函数
        '''I am dying.'''
        print '%s says bye.' % self.name

    def sayHi(self):
        '''Greeting by the person.

        Really.That all it does.'''
        print '''Hi,My name is %s''' % self.name

    def howmany(self):
        '''Print the current population.'''
        if Person.population == 1:
            print 'I am the only person.'
        else:
            print 'We have %d person here.' % Person.population

swaroop = Person('swaroop')
swaroop.sayHi()
swaroop.howmany()

kalam = Person('kalam')
kalam.sayHi()
kalam.howmany()

swaroop.sayHi()
swaroop.howmany()

结果：

 

 

C:\Python27\python.exe D:/PyTest_one/test.py
(Initializing swaroop)
Hi,My name is swaroop
I am the only person.
(Initializing kalam)
Hi,My name is kalam
We have 2 person here.
Hi,My name is swaroop
We have 2 person here.
kalam says bye.    #注意析构函数的顺序
swaroop says bye.

Process finished with exit code 0

类继承：

 

 

class schoolMember:
    '''Represents any school Member.'''
    def __init__(self,name,age):
        self.name = name
        self.age = age
        print '(Initialized SchoolMember: %s)' % self.name

    def tell(self):
        '''Tell my details.'''
        print 'Name:"%s", Age:"%s"' % (self.name,self.age)


class teacher(schoolMember):
    '''Represents a teacher.'''
    def __init__(self,name,age,salary):
        schoolMember.__init__(self,name,age)
        self.salary = salary
        print '(Initializing the teacher:%s)' %self.name

    def tell(self):
        schoolMember.tell(self)
        print 'Salary: "%d"' % self.salary

class student(schoolMember):
    '''Represents the students.'''
    def __init__(self,name,age,Mark):
        schoolMember.__init__(self,name,age)
        self.Mark = Mark
        print '(Initialing the student:%s)' %self.name

    def tell(self):
        schoolMember.tell(self)
        print 'Mark: "%d"' % self.Mark


t = teacher('Mrs.Zhang',38,5888)
s = student('zhang',18,2000)

print

members = [t,s]
for member in members:
    member.tell()

结果：

 

 

C:\Python27\python.exe D:/PyTest_one/test.py
(Initialized SchoolMember: Mrs.Zhang)
(Initializing the teacher:Mrs.Zhang)
(Initialized SchoolMember: zhang)
(Initialing the student:zhang)

Name:"Mrs.Zhang", Age:"38"
Salary: "5888"
Name:"zhang", Age:"18"
Mark: "2000"

Process finished with exit code 0

文件操作：

 

 

# coding=utf-8
poem = '''\
Programing is fun
When the work is done
if your wanna make your work also fun:
use python!
'''

f = file('poem.txt','w')#若不存在自动创建
f.write(poem)
f.close()

f = file('poem.txt')#默认模式为read
while True:
    line = f.readline()
    if len(line) == 0:
        break
    print line

f.close()

存储与去存储：

 

 

# coding=utf-8
import cPickle as p #给模块一个新名字
shoplistfile = 'shoplist.date'

shoplist = ['apple','mango','carrot']

f = file(shoplistfile,'w') #打开文件
p.dump(shoplist,f)#往该文件里写数据
f.close()

del shoplist#删除该程序中的shoplist变量

f = file(shoplistfile)#打开文件
storedlist = p.load(f)#下载文件中的数据
print  storedlist

异常：

 

 

#引发异常
# coding=utf-8
class ShortInputExcept(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 something-->')
    if len(s)<3:
        raise ShortInputExcept(len(s),3)
except EOFError:
    print 'Why did you do an EOF to me?'
except ShortInputExcept,x:#x为ShotInputExcept的一个实例，或者except ShortInputException as x
    print 'ShortInputException: The input was of length %d, \
     was expecting at least %d' % (x.length,x.atleast)
else:
    print 'No exception was raised.'
	
	
异常发生与否的情况下都关闭文件	
# coding=utf-8
import time
try:
    f = file('poem.txt')
    while True: # our usual file-reading idiom
        line = f.readline()
        if len(line) == 0:
            break
        time.sleep(2)
        print line,#多次输出不换行
finally:
    f.close()
    print 'Cleaning up...closed the file'
	
#问题：系统控制台执行时出问题：
C:\Users\Administrator>python D:\PyTest_one\test.py
Traceback (most recent call last):
  File "D:\PyTest_one\test.py", line 3, in 
    f = open('poem.txt')
IOError: [Errno 2] No such file or directory: 'poem.txt'

模块：

 

sys
# coding=utf-8
import sys
def readfile(filename):
    '''Print a file to the standard output.'''
    f = file(filename)
    while True:
        line = f.readline()
        if len(line) == 0:
            break
        print line, # notice comma
    f.close()

if len(sys.argv) < 2:
    print 'No action specified.'
    sys.exit()

if sys.argv[1].startswith('--'):#如果第二个参数是以--开头
    option = sys.argv[1][2:]#选择--之后的字符
    if option == 'version':
        print 'Version 1.2'
    elif option == 'help':
        print '''\
        This program prints files to the standard output.
        Any number of files can be specified.
        Options include:
        --version : Prints the version number
        --help : Display this help'''
    else:
        print 'Unknown option.'
    sys.exit()
else:
    for filename in sys.argv[1:]:#如果后面直接跟的是文件名，则输出
        readfile(filename)

结果：

 

C:\Users\Administrator>python D:\PyTest_one\test.py --help
        This program prints files to the standard output.
        Any number of files can be specified.
        Options include:
        --version : Prints the version number
        --help : Display this help

C:\Users\Administrator>python D:\PyTest_one\test.py D:\PyTest_one\poem.txt
Programing is fun
When the work is done
if your wanna make your work also fun:
use python!

查询python版本信息：

 

 

C:\Users\Administrator>python
Python 2.7.12 (v2.7.12:d33e0cf91556, Jun 27 2016, 15:19:22) [MSC v.1500 32 bit (
Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.version
'2.7.12 (v2.7.12:d33e0cf91556, Jun 27 2016, 15:19:22) [MSC v.1500 32 bit (Intel)
]'
>>> sys.version_info
sys.version_info(major=2, minor=7, micro=12, releaselevel='final', serial=0)

 

 

模块：os


● os.name字符串指示你正在使用的平台。比如对于Windows，它是'nt'，而对于Linux/Unix
用户，它是'posix'。
● os.getcwd()函数得到当前工作目录，即当前Python脚本工作的目录路径。
● os.getenv()和os.putenv()函数分别用来读取和设置环境变量。
● os.listdir()返回指定目录下的所有文件和目录名。
● os.remove()函数用来删除一个文件。
● os.system()函数用来运行shell命令。
● os.linesep字符串给出当前平台使用的行终止符。例如，Windows使用'\r\n'，Linux使
用'\n'而Mac使用'\r'。
● os.path.split()函数返回一个路径的目录名和文件名。
>>> os.path.split('/home/swaroop/byte/code/poem.txt')
('/home/swaroop/byte/code', 'poem.txt')
● os.path.isfile()和os.path.isdir()函数分别检验给出的路径是一个文件还是目录。类似地，os.
path.exists()函数用来检验给出的路径是否真地存在。


结果：

 

 

 

 

C:\Users\Administrator>python
Python 2.7.12 (v2.7.12:d33e0cf91556, Jun 27 2016, 15:19:22) [MSC v.1500 32 bit (
Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.name
'nt'
>>> os.getcwd

>>> os.getcwd()
'C:\\Users\\Administrator'
>>> os.listdir('C:\\Users\\Administrator')
['.aliyun', '.android', '.idlerc', '.ipynb_checkpoints', '.ipython', '.jupyter',
 '.oracle_jre_usage', '.PyCharm2016.3', '.WebStorm10', 'AppData', 'Application D
ata', 'Contacts', 'Cookies', 'Desktop', 'Documents', 'Downloads', 'fancy', 'Favo
rites', 'Funshion', 'FunShion.ini', 'hsKfLshPLQ9', 'IntelGraphicsProfiles', 'Lin
ks', 'Local Settings', 'Music', 'My Documents', 'NetHood', 'NTUSER.DAT', 'ntuser
.dat.LOG1', 'ntuser.dat.LOG2', 'NTUSER.DAT{bbed3e3b-0b41-11e3-8249-d6927d06400b}
.TM.blf', 'NTUSER.DAT{bbed3e3b-0b41-11e3-8249-d6927d06400b}.TMContainer000000000
00000000001.regtrans-ms', 'NTUSER.DAT{bbed3e3b-0b41-11e3-8249-d6927d06400b}.TMCo
ntainer00000000000000000002.regtrans-ms', 'ntuser.ini', 'Pictures', 'PrintHood',
 'qms-bmh1.bmp', 'qms-bmh2.bmp', 'qms-bmh3.bmp', 'quartus2.ini', 'quartus2.qreg'
, 'quartus_full_rules_file.txt', 'quartus_web_rules_file.txt', 'Recent', 'Saved
Games', 'Searches', 'SelfFiles.pfx', 'SendTo', 'Templates', 'Untitled.ipynb', 'u
ntitled.txt', 'Untitled1.ipynb', 'Videos', '\xa1\xb8\xbf\xaa\xca\xbc\xa1\xb9\xb2
\xcb\xb5\xa5']
>>> os.system('exit')
0
>>> os.linesep
'\r\n'
>>> os.path.split('D:\\PyTest_one\\test.py')
('D:\\PyTest_one', 'test.py')
>>> os.path.exists('D:\\PyTest_one')
True

其他知识：

 

#列表综合：
# coding=utf-8
listone = [2,3,4]
listtwo = [2*i for i in listone if i>2]
print listtwo

#结果：
C:\Python27\python.exe D:/PyTest_one/test.py
[6, 8]

Process finished with exit code 0


#在函数中接受元组和列表：
def powersum(power, *args):
    '''Return the sum of each argument raised to specified power.'''
    total = 0
    for i in args:
        total += pow(i, power)#返回i的power次方
    return total


print powersum(2,3,4)#多余的函数参数都会作为一个元组存储在args中
print powersum(2,5,6)

#结果：25 61

#lambda形式返回函数
# coding=utf-8
def make_repeater(n):
    return lambda s:s*n

twice = make_repeater(2)

print twice(2)
print twice('wwe')

#结果：
4
wwewwe

#exec和eval语句

# coding=utf-8
exec 'print "HELLO WORLD"'#计算字符串或文件中的Pyhton语句
print eval('2*3')#计算字符串或文件中的有效表达式

assert语句：

mylist = ['item']
assert len(mylist) >= 1
mylist.pop()#移除列表中最后一个元素
print mylist
assert len(mylist) >1#引发AssertionError错误