Detailed explanation of how to use python's property syntax

There is a property syntax in Python, which is similar to C#'s get set syntax. Its functions have the following two points:

Set class methods as read-only properties;

Implement properties getter and setter methods;

The following focuses on these two points:

Set the class method as a read-only attribute

Please read the following code first

class Book(object):
    def __init__(self, title, author, pub_date):
        self.title = title
        self.author = author
        self.pub_date = pub_date
 
    @property
    def des_message(self):
        return u'书名：%s， 作者：%s， 出版日期：%s' % (self.title, self.author, self.pub_date)

In this code, use property as a decorator to modify the des_message function. Its function is to turn the function des_message into a property of the class, and it is read-only. The effect is as follows:

#As shown in the figure above, the method becomes a property, which can be accessed by accessing properties. But if you modify its value, an AttributeError error will be reported. It is read-only

Implement the getter and setter methods of the attribute

Then check the following code:

class Array(object):
 
    def __init__(self, length=0, base_index=0):
        assert length >= 0
        self._data = [None for i in xrange(length)]
        self._base_index = base_index
         
    def get_base_index(self):
        return self._base_index
 
    def set_base_index(self, base_index):
        self._base_index = base_index
 
    base_index = property(
        fget=lambda self: self.get_base_index(),
        fset=lambda self, value: self.set_base_index(value)
    )

Here We set a base_index attribute for class Array, which uses property to implement the fget and fset functions of base_index. base_index is readable and writable. The effect is as follows:

As shown above As shown, base_index is readable and writable.

Finally

property is a good syntax feature of Python, and we should use it frequently in programming.

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