Call a Function with clicked Item from QListWidgetItem in Python

I am using Qt-designer and PyQt. I set up a Window with some Buttons and a QListWidget.

I want to get the clicked item of a QListWidget. For example I have 4 Items in the List and I click the first one the item should be sent to another function.

I read some examples but they always use classes and "self". Since I am a total newbie I want to start simple and set everything up without a class.

def show_item(item):
    print (item)

mainscreen.connect(mainscreen.myList, SIGNAL("itemClicked(QListWidgetItem*)"),QListWidgetItem, showItem(QListWidgetItem))

I don't really understand those errors since I thought all of the requirements are fullfilled.

TypeError: arguments did not match any overloaded call:
  QObject.connect(QObject, SIGNAL(), QObject, SLOT(), Qt.ConnectionType=Qt.AutoConnection): argument 3 has unexpected type 'PyQt4.QtCore.pyqtWrapperType'
  QObject.connect(QObject, SIGNAL(), callable, Qt.ConnectionType=Qt.AutoConnection): argument 4 has unexpected type 'str'
  QObject.connect(QObject, SIGNAL(), SLOT(), Qt.ConnectionType=Qt.AutoConnection): argument 3 has unexpected type 'PyQt4.QtCore.pyqtWrapperType'

Edit: Code Sample

import sys
from PyQt4.QtCore import *
from PyQt4.QtGui import *
from PyQt4.uic import 

def show_item(item):
    print (item)



for x in range(4):
    mainscreen.mylist_sorted.addItem(x)

app = QApplication(sys.argv)
mainscreen = loadUi("mainscreen.ui")
mainscreen.connect(mainscreen.mylist_sorted, SIGNAL("itemClicked(QListWidgetItem*)"),QListWidgetItem, (showItem(QListWidgetItem)))
mainscreen.show()
sys.exit(app.exec_())

mainscreen.ui file

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>mainscreen</class>
 <widget class="QMainWindow" name="mainscreen">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>800</width>
    <height>600</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <widget class="QListWidget" name="mylist_sorted">
    <property name="geometry">
     <rect>
      <x>30</x>
      <y>160</y>
      <width>256</width>
      <height>192</height>
     </rect>
    </property>
   </widget>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>800</width>
     <height>25</height>
    </rect>
   </property>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
 </widget>
 <resources/>
 <connections/>
</ui>

Solution

Your code has the following errors:

The name of the QListWidget is mylist_sorted, and not mylist as you are using it.
If you are going to connect with a function you must use the seconde signature: QObject.connect(QObject, SIGNAL(), callable, Qt.ConnectionType=Qt.AutoConnection) where the third parameter is the function.
The name of the function is show_item, it is not showItem. It is the second error of the same type, that is, with the name of the variables. In Python it is very important that the name used be the same as the one that was declared.

Considering the above the solution is:

import sys
from PyQt4.QtCore import SIGNAL
from PyQt4.QtGui import QApplication, QListWidgetItem
from PyQt4.uic import loadUi


def show_item(item):
    print(item)


if __name__ == "__main__":

    app = QApplication(sys.argv)
    mainscreen = loadUi("mainscreen.ui")
    for x in range(4):
        mainscreen.mylist_sorted.addItem(str(x))

    mainscreen.connect(
        mainscreen.mylist_sorted,
        SIGNAL("itemClicked(QListWidgetItem*)"),
        show_item,
    )
    mainscreen.show()
    sys.exit(app.exec_())

Although it is advisable to use the new connection syntax:

import sys
from PyQt4.QtCore import SIGNAL
from PyQt4.QtGui import QApplication, QListWidgetItem
from PyQt4.uic import loadUi


def show_item(item):
    print(item)


if __name__ == "__main__":

    app = QApplication(sys.argv)
    mainscreen = loadUi("mainscreen.ui")
    for x in range(4):
        mainscreen.mylist_sorted.addItem(str(x))

    mainscreen.mylist_sorted.itemClicked.connect(show_item)
    mainscreen.show()
    sys.exit(app.exec_())