python @property的介绍与使用
python的@property是python的一种装饰器,是用来修饰方法的。
作用:
我们可以使用@property装饰器来创建只读属性,@property装饰器会将方法转换为相同名称的只读属性,可以与所定义的属性配合使用,这样可以防止属性被修改。
使用场景:
1.修饰方法,是方法可以像属性一样访问。
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<span class="k">class <span class="nc">DataSet<span class="p">(<span class="nb">object<span class="p">): <span class="nd">@property <span class="k">def <span class="nf">method_with_property<span class="p">(<span class="bp">self<span class="p">): <span class="c1">##含有@property <span class="k">return <span class="mi">15 <span class="k">def <span class="nf">method_without_property<span class="p">(<span class="bp">self<span class="p">): <span class="c1">##不含@property <span class="k">return <span class="mi">15 <span class="n">l <span class="o">= <span class="n">DataSet<span class="p">() <span class="k">print<span class="p">(<span class="n">l<span class="o">.<span class="n">method_with_property<span class="p">) <span class="c1"># 加了@property后,可以用调用属性的形式来调用方法,后面不需要加()。 <span class="k">print<span class="p">(<span class="n">l<span class="o">.<span class="n">method_without_property<span class="p">()) <span class="c1">#没有加@property , 必须使用正常的调用方法的形式,即在后面加()</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span> |
两个都输出为15。
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<span class="k">class <span class="nc">DataSet<span class="p">(<span class="nb">object<span class="p">): <span class="nd">@property <span class="k">def <span class="nf">method_with_property<span class="p">(<span class="bp">self<span class="p">): <span class="c1">##含有@property <span class="k">return <span class="mi">15 <span class="n">l <span class="o">= <span class="n">DataSet<span class="p">() <span class="k">print<span class="p">(<span class="n">l<span class="o">.<span class="n">method_with_property<span class="err">()<span class="p">) <span class="c1"># 加了@property后,可以用调用属性的形式来调用方法,后面不需要加()。</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span> |
如果使用property进行修饰后,又在调用的时候,方法后面添加了(), 那么就会显示错误信息:TypeError: ‘int’ object is not callable,也就是说添加@property 后,这个方法就变成了一个属性,如果后面加入了(),那么就是当作函数来调用,而它却不是callable(可调用)的。
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<span class="k">class <span class="nc">DataSet<span class="p">(<span class="nb">object<span class="p">): <span class="k">def <span class="nf">method_without_property<span class="p">(<span class="bp">self<span class="p">): <span class="c1">##不含@property <span class="k">return <span class="mi">15 <span class="n">l <span class="o">= <span class="n">DataSet<span class="p">() <span class="k">print<span class="p">(<span class="n">l<span class="o">.<span class="n">method_without_property<span class="err">) <span class="c1">#没有加@property , 必须使用正常的调用方法的形式,即在后面加()</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span> |
没有使用property修饰,它是一种方法,如果把括号去掉,不会报错输出的就会是方法存放的地址。
2.与所定义的属性配合使用,这样可以防止属性被修改。
由于python进行属性的定义时,没办法设置私有属性,因此要通过@property的方法来进行设置。这样可以隐藏属性名,让用户进行使用的时候无法随意修改。
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<span class="k">class <span class="nc">DataSet<span class="p">(<span class="nb">object<span class="p">): <span class="k">def <span class="fm">__init__<span class="p">(<span class="bp">self<span class="p">): <span class="bp">self<span class="o">.<span class="n">_images <span class="o">= <span class="mi">1 <span class="bp">self<span class="o">.<span class="n">_labels <span class="o">= <span class="mi">2 <span class="c1">#定义属性的名称 <span class="nd">@property <span class="k">def <span class="nf">images<span class="p">(<span class="bp">self<span class="p">): <span class="c1">#方法加入@property后,这个方法相当于一个属性,这个属性可以让用户进行使用,而且用户有没办法随意修改。 <span class="k">return <span class="bp">self<span class="o">.<span class="n">_images <span class="nd">@property <span class="k">def <span class="nf">labels<span class="p">(<span class="bp">self<span class="p">): <span class="k">return <span class="bp">self<span class="o">.<span class="n">_labels <span class="n">l <span class="o">= <span class="n">DataSet<span class="p">() <span class="c1">#用户进行属性调用的时候,直接调用images即可,而不用知道属性名_images,因此用户无法更改属性,从而保护了类的属性。 <span class="k">print<span class="p">(<span class="n">l<span class="o">.<span class="n">images<span class="p">) <span class="c1"># 加了@property后,可以用调用属性的形式来调用方法,后面不需要加()。</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span> |