Python学习第十二天

摘要: 今天学习了下 异常处理 以及class对象

#!/usr/bin/python

#filename:test12.py

while True :

try :

x = int ( input ("please enter a number:"))

break

except ValueError :

print ("Oops! That was no valid number. Try again...")

import sys

try :

f = open ("myfile.txt")

s = f.readline()

i = int(s.strip())

except OSError as err :

print ("OS error: {0}".format(err))

except ValueError :

print ("Could not convert data to a integer.")

except :

print ("Unexcepted error:",sys.exc_info()[0])

raise

print (sys.argv[1:])

for arg in sys.argv[1:]:

try:

f = open (arg,'r')

except IOError:

print('cannot open',arg)

else:

print(arg,'has',len(f.readlines()),'lines')

f.close()

def this_fails():

x = 1/0

try:

this_fails()

except ZeroDivisionError as err:

print ("handling run-time error:",err)

try:

raise NameError('HiThere')

except NameError:

print ("An exception flew by!")

raise

class MyError(Exception):

def __init__(self,value):

self.value = value

def __str__(self):

return repr(self.value)

try:

raise MyError(2*2)

except MyError as e:

print ("My exception occurred ,value:",e.value)

f.close()

#!/usr/bin/python

#filename:test12_2.py

def divide(x,y) :

try:

result = x / y

except ZeroDivisionError:

print ("division by zero !")

else:

print ("result is",result)

finally:

print ("executing finally clause")

divide(2,1) #success

divide(2,0) #exception

#divide("2","1") #uncaught error

for line in open("myfile.txt"):

print (line,end="")

with open("myfile.txt") as f :

for line in f:

print (line,end="")

#!/usr/bin/python

#filename: test12_3.py

def scope_test():

def do_local():

spam = "local spam"

def do_nonlocal():

nonlocal spam

spam = "nonlocal spam"

def do_global():

global spam

spam = "global spam"

spam = "test spam"

do_local()

print ("After local assignment:",spam)

do_nonlocal()

print ("After nonlocal assignment:",spam)

do_global()

print ("After global assignment:",spam)

scope_test()

print ("In global scope:",spam)

class MyClass:

i = 12345

def f(self):

return "hello world"

x = MyClass()

print (x.i)

print (x.f())

xf = x.f

#while True:

#print (xf()) #this is a endless loop

class Complex:

def __init__(self,realpart,imagpart):

self.r = realpart

self.i = imagpart

x = Complex(1,2)

print (x.r)

print (x.i)

x.counter = 1

while x.counter < 10:

x.counter = x.counter * 2

print (x.counter)

del x.counter

class Dog:

kind = 'canine'

tricks = []

def __init__(self,name):

self.name = name

self.tricks1 = []

def add_trick(self,trick):

self.tricks.append(trick)

self.tricks1.append(trick)

d = Dog('Fido')

e = Dog('Buddy')

print (d.kind)

print (e.kind)

print (d.name)

print (e.name)

d.add_trick("roll over")

e.add_trick("play dead")

print(d.tricks)

print(e.tricks)

print(d.tricks1)

print(e.tricks1)