Providing a list to a function

June 8, 2024

I’ve never come across this problem until now and can’t think how to proceed.
I would like to know how to provide each element of a list to a function that wants individual parameters:

list = (1,2,3,4)

def myFunction(w, x, y, z):

but calling it with:

u = myFunction(list)

This is probably beside the point, but the application has to do with drawing with PyQt’s QPainter and providing the coordinates in a list (mylist, in the code below):

#!/usr/bin/python3
import sys
from PyQt5.QtWidgets import QLabel, QMainWindow, QApplication
from PyQt5.QtCore import Qt
from PyQt5.QtGui import QPainter, QPixmap

class MyWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        lbl = QLabel()
        pm = QPixmap(70, 70)
        pm.fill(Qt.white)
        lbl.setPixmap(pm)
        self.setCentralWidget(lbl)
        p = QPainter(lbl.pixmap())
        p.drawLine(10,20,10,40)
        line = (10,40, 40, 50)
        p.drawLine(line)
        p.end()
        self.show()

app = QApplication(sys.argv)
win = MyWindow()
app.exec_()

Thank you for any help.

>Solution :

You can change p.drawLine(line) to p.drawLine(*line).
Also, you probably want to pass the line as a list() not tuple() (note that list = (1,2,3,4) is not a list().):

#!/usr/bin/python3
import sys
from PyQt5.QtWidgets import QLabel, QMainWindow, QApplication
from PyQt5.QtCore import Qt
from PyQt5.QtGui import QPainter, QPixmap

class MyWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        lbl = QLabel()
        pm = QPixmap(70, 70)
        pm.fill(Qt.white)
        lbl.setPixmap(pm)
        self.setCentralWidget(lbl)
        p = QPainter(lbl.pixmap())
        p.drawLine(10,20,10,40)
        line = [10,40, 40, 50]
        p.drawLine(*line)
        p.end()
        self.show()

app = QApplication(sys.argv)
win = MyWindow()
app.exec_()