在Python中将原始数据类型名称作为函数参数传递

Question

I'm java programmer trying to learn Python and as a result I'm trying to relate both the languages.

Recently I started working with PyQt5 library. I'm following a tutorial on udemy where we used

custom_signal = pyqtSignal(str)

then in our slot the data comes in as string. If we use

custom_signal = pyqtSignal(int)

then data will be passed as an integer to slot.

Could anyone explain me what's happening internally. Why we are passing datatype name to constructor of a class (pyqtSignal(int)). Is it related to something like Generic types in java?

List<Integer> list = new ArrayList<Integer>();

As the above variable only accepts integers, pyqtSignal(int) also is similar to that?

Could someone throw some light on that. This may be silly, but I just wanted to understand whats happening inside. I tried to watch the source code of pyqtSignal class but I was not able to find the same online anywhere.

Also could anyone please tell me object creation process that happens internally like what special methods (_new_, _init_ etc..) are called and in what sequence for what purpose.

Thanks in advance

Answer 1

The pyqtSignal is in reality a factory that produces a new signal with the parameters you passed.

The definition of the factory method is as follows:

PyQt5.QtCore.pyqtSignal(types[, name[, revision=0[, arguments=[]]]])

Meaning if you want to define a signal called rangeChanged that takes two integer arguments you'd do the below:

range_changed = pyqtSignal(int, int, name='rangeChanged')

You can read more about this factory here .

In regards to the dunder methods ( __ name __ ) or otherwise known as magic methods - A good explanation can be found here .