Python 3.x Learning Note 12 (reflection and exception)

1. Reflection
Mapping or modifying the state, properties, methods of a program while it is running through a string

GetAttr (OBJ,NAME_STR): Gets the memory address of the corresponding method in the Obj object according to the string name_str

Hasttr (OBJ,NAME_STR): A way to determine if an object in obj has a corresponding string

SetAttr (obj, ' y ', z): The SetAttr function corresponds to the function Getatt (), which is used to set the property value, which must exist.

Delattr (obj, ' y '): Removes the named property from the given object

classDog (object):def __init__(self,name): Self.name=namedefEat (self):Print('%s is eating ....'%self.name) d= Dog ('Xiaohei')#instantiating an objectChoice = input ('>>>>:'). Strip ()#strip () remove left and right spacesifHasattr (D,choice):#Check that instantiation D has no choiceFunc = GetAttr (D,choice)#GetAttr Returns the memory address of the choice in DFunc ()#Execute function

2. Exception Basics

In the programming process in order to increase the friendliness of the program in the event of a bug will not be displayed to the user error message, but the reality of a hint of the page, popular is not to let users see the big Yellow Pages.

1) Basic structure

Try : Pass except Exception as E: Pass

2) Other structures

 #   exception structure    Try  :  #   Main code block  pass  except   Keyerror as E:  #   When an exception is executed, the block  pass  else  :  #      The main code block executes, that is, no exception, executes the block  pass  finally  :  #      pass  

3) proactively triggering exceptions

Try :     Raise Exception (' error ... ' )except  Exception as E:    print(e)

3. Common types of anomalies
Attributeerror #试图访问一个对象没有的树形, such as foo.x, but Foo has no attribute x
IOError #输入/Output exception: Basically, the file cannot be opened
Importerror # cannot introduce modules or packages; it's basically a path problem or a name error
Indentationerror #语法错误 (subclass); The code is not aligned correctly
Indexerror #下标索引超出序列边界, such as when X has only three elements, but tries to access X[5]
Keyerror # Trying to access keys that don't exist in the dictionary
Keyboardinterrupt # CTRL + C is pressed
Nameerror # using a variable that has not been assigned to an object
SyntaxError # python code is illegal, code cannot compile (personally think this is a syntax error, write wrong)
TypeError # Incoming object type does not conform to the requirements
Unboundlocalerror # attempts to access a local variable that has not yet been set, basically because another global variable with the same name causes you to think that you are accessing it
ValueError # Passes in a value that is not expected by the caller, even if the value is of the correct type

Python 3.x Learning Note 12 (reflection and exception)