Can I utilize Pyside clicked.connect to connect a function which has a parameter

Question

I want to have a function in main class which has parameters not only self.

class Ui_Form(object):
    def clearTextEdit(self, x):
            self.plainTextEdit.setPlainText(" ")
            print("Script in Textbox is Cleaned!",)

x will be my additional parameter and I want clearTextEdit to be called by click.

self.pushButton_3.clicked.connect(self.clearTextEdit(x))

it does not allow me to write x as parameter in clicked. Can you help me!

Marcellusmarcelo

Answer 1

Solution

This is a perfect place to use a lambda:

self.pushButton_3.clicked.connect(lambda: self.clearTextEdit(x))

Remember, connect expects a function of no arguments, so we have to wrap up the function call in another function.

Explanation

Your original statement

self.pushButton_3.clicked.connect(self.clearTextEdit(x))  # Incorrect

was actually calling self.clearTextEdit(x) when you made the call to connect, and then you got an error because clearTextEdit doesn't return a function of no arguments, which is what connect wanted.

Lambda?

Instead, by passing lambda: self.clearTextEdit(x), we give connect a function of no arguments, which when called, will call self.clearTextEdit(x). The code above is equivalent to

def callback():
    return self.clearTextEdit(x)
self.pushButton_3.clicked.connect(callback)

But with a lambda, we don't have to name "callback", we just pass it in directly.

If you want to know more about lambda functions, you can check out this question for more detail.

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On an unrelated note, I notice that you don't use x anywhere in clearTextEdit. Is it necessary for clearTextEdit to take an argument in the first place?

Jacindajacinta

thank you Istvan, you made my code more readable and less complex:) Let me ask you one more questıon: what if I have another function and I want to add that function as a parameter in my original function. such as: def myFunct(): return x and self.pushButton_3.clicked.connect(lambda:self.clearTextEdit(clearTextEdit(myFunct))) is it allowed in pyside?? Thanks in advance – Marcellusmarcelo

By the way, I just needed an example so that I could do in my project. writing whole script would be garbage I guess. I would thank u a lot. my duty is done :) – Marcellusmarcelo

@Marcellusmarcelo Yes, that can be done in the same way as passing any other argument. Your example would look something like self.pushButton_3.clicked.connect(lambda: self.clearTextEdit(myFunct)) (you had an extra clearTextEdit) – Jacindajacinta