Class 定义 required_arg, *args, **kwargs

Question

我想使用一个 required_arg 除了 *args，**kwargs 在来自另一个 class 的 class 中。但是目前我没有成功！！！这段代码：

class PageNumCanvas(canvas.Canvas):
    "For  add \"page number of total\" in each footer."

    def __init__(self, page1, *args, **kwargs):
        "Constructor."
        self.page1 = page1 - 1
        canvas.Canvas.__init__(self, *args, **kwargs)
        self.pages = []

我这样做时的错误信息：canvasmaker = PageNumCanvas(1):

canvas.Canvas.__init__(self, *args, **kwargs)
    TypeError: __init__() takes at least 2 arguments (1 given)

如何使用 page1 参数调用 PageNumCanvas class？

更新 #1：

如果我在 class 的 init 中不使用参数，我没有问题。例如：

>>> from reportlab.pdfgen import canvas
>>> class PageNumCanvas(canvas.Canvas):
...     "For  add \"page number of total\" in each footer."
...     def __init__(self, *args, **kwargs):
...             canvas.Canvas.__init__(self, *args, **kwargs)
...             self.pages = []
... 
>>> canvasmaker = PageNumCanvas(1)
>>> canvasmaker
<__main__.PageNumCanvas instance at 0x7f618195df38>
>>>

更新 #2：感谢 goncalopp 的指路，正确的代码是：

class PageNumCanvas(canvas.Canvas):
...     "For  add \"page number of total\" in each footer."
...     def __init__(self, page1, *args, **kwargs):
...             "Constructor."
...             canvas.Canvas.__init__(self, page1, *args, **kwargs)
...             self.page1 = page1 - 1
...             self.pages = []
...             print self.page1
... 
>>> canvasmaker = PageNumCanvas(12)
11
>>>

Answer 1

您可能正在寻找

canvas.Canvas.__init__(self, page1, *args, **kwargs)

Answer 2

根据示例here，您需要在实例化时提供名称canvas.Canvas()。

你的第二个版本没有给你错误的原因是你仍在传递 1 ，它被传递给 Canvas 构造函数，因为你删除了 page1 参数.

为了使其正常工作，您只需输入名称和页码即可：

from reportlab.pdfgen import canvas
class PageNumCanvas(canvas.Canvas):
    "For  add \"page number of total\" in each footer."

    def __init__(self, page1, *args, **kwargs):
        "Constructor."
        self.page1 = page1 - 1
        canvas.Canvas.__init__(self, *args, **kwargs)
        self.pages = []

canvasmaker = PageNumCanvas(1, "Hello.pdf")
print canvasmaker.page1

输出

Class 定义 required_arg, *args, **kwargs

Class definition with required_arg, *args, **kwargs

python

arguments

class