Python basic error-prone problem

1. Enter what the following code:

class Person :     = 1    def__init__(self):        pass    def  getage (self):         Print (__name__= Person () p.getage ()

The result is:

__main__

2. What code do I need to add in order to run this code?

 class   A (object):  def  __init__   (self,a,b): self.
    __a  = a self.  __b  = b  def< /span> Myprint (self):  print ( "  a=   ", Self.__a ,  " b=  Span style= "COLOR: #800000" > ", self. __b)   A1  =a (10,20) 

The answer is:

classA (object):def __init__(self, A, b): Self.__a=a self.__b=bdefMyprint (self):Print ('a=', self.__a,'b=', self.__b)    def __call__(self, num):Print ('Call :', num + self.__a)

3. What does the following code enter?

classB (object):deffn (self):Print ('B fn')    def __init__(self):Print ("B INIT")  classA (object):deffn (self):Print ('A fn')     def __new__(cls,a):Print（"NEW", a)ifA>10:                returnSuper (A, CLS).__new__(CLS)returnB ()def __init__(self,a):Print ("INIT", a) A1= A (5) A1.fn () A2=a (20) A2.fn ()

The answer is:

NEW 5A fn

4. Add code to run the following program and return the specified result

class A (object):     def __init__ (self,a,b):         = a        = b        print ('init')    def Mydefault (self):         Print ( ' default ')  = A (10,20) a1.fn1 () a1.fn2 () a1.fn3 ()

return Result:

Defaultdefaultdefault

The answer is: Add __getattr__ () Magic method

classA (object):def __init__(self,a,b): self.a1=a self.b1=bPrint（'Init')    defMydefault (self):Print ('default')    def __getattr__(self,name):returnSelf.mydefault A1= A (10,20) a1.fn1 () a1.fn2 () a1.fn3 ( )

Extended:

classA (object):def __init__(self, A, b): Self.a1=a self.b1=bPrint('Init')    defMydefault (Self, *args):Print('Default:'+str (args[0]))def __getattr__(self, name):Print("Other fn:", name)returnself.mydefaulta1= A (10, 20) a1.fn1 (33) a1.fn2 ('Hello') A1.fn3 (10)

The output is:

initother fn:fn1default:fn:fn2default:helloother fn:fn3default:10

5. There are three modules in a package, mod1.py, mod2.py, mod3.py, but how to ensure that only mod1 and mod3 are imported when using the From demopack import * module.

Answer: Add the __init__.py file and add it in the file:

__all__ = ['mod1','mod3']

6. Write a function that receives an integer parameter n and returns a function that multiplies the function's arguments and N and returns the result.

def Mulby (num):     def GN (val):         return num * val     return  gn  = Mulby (7)print(ZW ( 9));

7. Parse the code below where it's slow

def strtest1 (num):    str='first'     for inch range (num):        str+ ="X"    return Str    

Answer: Python's str is an immutable object, and each iteration generates a new STR object to store the new string, the larger the NUM, the more STR objects are created, and the more memory is consumed.

8. The following code:

class A (object):     def Show (self):         Print ' Base Show ' class B (A):     def Show (self):         Print ' Derived show '  = B () obj.show ()

How to call the Show method of Class A.
Here's how:

obj.__class__ =

The __class__ method points to the class object, only assigns a value type A to him, and then calls the method show, but when it is done, remember to change it back.

Python basic error-prone problem