How to use Python regular expressions for reflective programming

Regular Expression (Regular Expression) is a powerful string matching tool. The re module in Python provides support for regular expressions. Regular expressions can be used not only for string matching, but also for reflective programming, i.e. dynamically calling functions and properties. This article will introduce how to use Python regular expressions for reflective programming.

1. The concept of reflection

In Python, reflection refers to dynamically obtaining object information and calling the object's properties and methods when the program is running. Reflection can access objects in the form of strings and dynamically call methods and properties of objects. Objects in Python include modules, classes, instances, etc.

2. Use regular expressions to match object properties and methods

In reflective programming, it is very convenient to use regular expressions to match object properties and methods. Suppose we have an object obj with the following properties and methods:

class MyClass():
    a = "hello"
    def func(self):
        pass

We can use the dir() function to get all the properties and methods of obj:

obj = MyClass()
print(dir(obj))

This will output a list containing All properties and methods of obj.

If we want to use regular expressions to get all the properties and methods containing "e" in obj, we can use the filter() function and the re module to achieve it:

import re
obj = MyClass()
lst = [attr for attr in dir(obj) if re.search(r"e", attr)]
print(lst)

In this way, we can get obj All results containing "e" in the property and method names. If we want to match specific properties or methods, we can use the search() function, for example:

import re
obj = MyClass()
attr = "a"
method = "func"
if re.search(attr, dir(obj)):
    print(f"Found {attr}")
if re.search(method, dir(obj)):
    print(f"Found {method}")

3. Use regular expressions to call the properties and methods of the object

In addition to matching We can also use regular expressions to dynamically call the properties and methods of objects. Taking the above obj as an example, we can use regular expressions to call a specific attribute or method:

import re
obj = MyClass()
attr = "a"
method = "func"
if re.search(attr, dir(obj)):
    value = getattr(obj, attr)
    print(value)
if re.search(method, dir(obj)):
    func = getattr(obj, method)
    func()

In this way, we can dynamically obtain the value of attribute a of obj and call the method func. If you need to dynamically pass parameters, you can use forms like args and kwargs, for example:

import re
obj = MyClass()
method = "func"
args = [1, 2, 3]
kwargs = {"key": "value"}
if re.search(method, dir(obj)):
    func = getattr(obj, method)
    func(*args, **kwargs)

In this way, you can dynamically call the method func of the obj object and pass the corresponding parameters.

Summary

Python regular expressions are very useful in reflective programming, and can easily match and call the properties and methods of objects. Flexible reflective programming can be achieved by using the re module with functions such as dir(), getattr(), and setattr(). When using it, you need to pay attention to the syntax and matching rules of regular expressions, as well as the object type and naming conventions for attributes and methods.

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