Python-dir () function

Dir () function

English Description:

You can use the built-in Dir function to list the identifier for a module definition. Identifiers have functions, classes, and variables.

When you provide a module name for Dir (), it returns a list of the name of the module definition. If no argument is supplied, it returns a list of names defined in the current module.

First, let's take a look at using dir on the input sys module. We see that it contains a large list of attributes.

Next, we don't use it to pass parameters to the Dir function--by default, it returns the list of properties for the current module. Note that the input module is also part of the list.

To observe the function of Dir, we define a new variable A and assign it a value, and then we examine dir, and we observe that the same value is added to the list. We use the DEL statement to delete the variable/attribute in the current module, which is once again reflected in the output of Dir.

A note about Del--this statement is used to delete a variable/name after it is run. In this example, Del A, you will no longer be able to use the variable a--it as if it had never existed.

Version:

This function is supported in each version and is still available in Python3.

code example:

>>> Import struct>>> dir ()   # Show the names in the module namespace[' __builtins__ ', ' __doc__ ', ' __na me__ ', ' struct ']>>> dir (struct)   # show the names in the struct module[' struct ', ' __builtins__ ', ' __doc__ ', ' _ _file__ ', ' __name__ ', ' __package__ ', ' _clearcache ', ' calcsize ', ' Error ', ' pack ', ' pack_into ', ' unpack ', ' Unpack_from ']& Gt;>> class Shape (object):        def __dir__ (self):            return ["area", ' perimeter ', ' location ']>>> s = Shape () >>> dir (s) [' area ', ' perimeter ', ' location ']

English Description:

Dir ([Object])

Without arguments, return the list of names in the current local scope. With an argument, attempt to return a list of valid attributes for that object.

If the object has a method named __dir__ (), this method would be called and must return the list of attributes. This allows objects, implement a custom __getattr__ () or __getattribute__ () function to customize the by Dir () report s their attributes.

If The object does not provide __dir__ (), the function tries its best to gather information from the object ' s __dict__ att Ribute, if defined, and from its type object. The resulting list is not necessarily complete, and could be inaccurate if the object has a custom __getattr__ ().

The default dir () mechanism behaves differently with different types of objects, as it attempts-produce the most Releva NT, rather than complete, information:

If the object is a module object, the list contains the names of the module ' s attributes.

If The object is a type or class object, the list contains the names of its attributes, and recursively of the attributes of its bases.

Otherwise, the list contains the object ' s attributes ' names, the names of its class ' s attributes, and recursively of the A Ttributes of its class ' s base classes.

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