PyQT and Qwt read data and plot -- not able to plot

**diedro** · 1st August 2014, 15:31

Dear all,
I am new in this forum and I am also new in the PyQT-QT-Qwt environment.
I am trying to write a program in PyQT and Qwt that should read the data from a file ant then plot it.
Unfortunately the pram does not work and I don't know why.

This is my code:
There is a button (pushButton_1) that open a folder where I can select a file.
The button pushButton_1 calls the def showDialog(self): action that open the folder and then plot the data. This is the point, I am not able to plot the data.

This is my full code. It is no so long, so I post the entire code. I hope that is OK for the administrator.

Qt Code:

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import numpy as np
from PyQt4 import QtCore, QtGui
import PyQt4.Qwt5 as Qwt
import sys, os, csv
from PyQt4.QtCore import *
from PyQt4.QtGui import *
import random
 
 
try:
    _fromUtf8 = QtCore.QString.fromUtf8
except AttributeError:
    def _fromUtf8(s):
        return s
 
try:
    _encoding = QtGui.QApplication.UnicodeUTF8
    def _translate(context, text, disambig):
        return QtGui.QApplication.translate(context, text, disambig, _encoding)
except AttributeError:
    def _translate(context, text, disambig):
        return QtGui.QApplication.translate(context, text, disambig)
 
class Ui_MainWindow(QtGui.QMainWindow):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName(_fromUtf8("MainWindow"))
        MainWindow.resize(800, 663)
        self.centralwidget = QtGui.QWidget(MainWindow)
        self.centralwidget.setObjectName(_fromUtf8("centralwidget"))
 
 
 
        self.pushButton_1 = QtGui.QPushButton(self.centralwidget)
        self.pushButton_1.setGeometry(QtCore.QRect(60, 20, 311, 27))
        self.pushButton_1.setObjectName(_fromUtf8("pushButton_1"))
        self.pushButton_2 = QtGui.QPushButton(self.centralwidget)
        self.pushButton_2.setGeometry(QtCore.QRect(60, 70, 311, 27))
        self.pushButton_2.setObjectName(_fromUtf8("pushButton_2"))
 
 
 
        self.qwtPlot_2 = Qwt.QwtPlot(self.centralwidget)
        self.qwtPlot_2.setGeometry(QtCore.QRect(60, 170, 400, 200))
        self.qwtPlot_2.setObjectName(_fromUtf8("qwtPlot_2"))
        self.qwtPlot_2.setAxisTitle(Qwt.QwtPlot.xBottom, 'x -->')
        self.qwtPlot_2.setAxisTitle(Qwt.QwtPlot.yLeft, 'y -->')
        grid = Qwt.QwtPlotGrid()
        pen = QPen(Qt.DotLine)
        pen.setColor(Qt.black)
        pen.setWidth(0)
        grid.setPen(pen)
        grid.attach(self.qwtPlot_2)
 
        self.qwtPlot_3 = Qwt.QwtPlot(self.centralwidget)
        self.qwtPlot_3.setGeometry(QtCore.QRect(60, 390, 400, 200))
        self.qwtPlot_3.setObjectName(_fromUtf8("qwtPlot_3"))
        self.qwtPlot_3.setAxisTitle(Qwt.QwtPlot.xBottom, 'x -->')
        self.qwtPlot_3.setAxisTitle(Qwt.QwtPlot.yLeft, 'y -->') 
        grid = Qwt.QwtPlotGrid()
        pen = QPen(Qt.DotLine)
        pen.setColor(Qt.black)
        pen.setWidth(0)
        grid.setPen(pen)
        grid.attach(self.qwtPlot_3)
 
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtGui.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 800, 25))
        self.menubar.setObjectName(_fromUtf8("menubar"))
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtGui.QStatusBar(MainWindow)
        self.statusbar.setObjectName(_fromUtf8("statusbar"))
        MainWindow.setStatusBar(self.statusbar)
 
        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)
 
 
        self.centralwidget.connect(self.pushButton_1, QtCore.SIGNAL('clicked()'), self.showDialog)    
 
 
 
    def retranslateUi(self, MainWindow):
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow", None))
        self.pushButton_1.setText(_translate("MainWindow", "Selec file txt", None))
        self.pushButton_2.setText(_translate("MainWindow", "Plot", None))
 
    #------------------------------------------------------------------------
              #azione apertura file0
    #------------------------------------------------------------------------              
    def showDialog(self):
           fname = QtGui.QFileDialog.getOpenFileName(self, 'Open a data file', '.', 'txt files (*.txt);;All Files (*.*)')
           f = open(fname, 'r')
           with f:
            data = np.genfromtxt(f, skiprows=1)
            self.tdata = data[:,0]
            self.cdata = data[:,1]
            curve=Qwt.QwtPlotCurve('ciao')
            curve.setData(range(len(self.tdata)), self.tdata)
            curve.attach(self.qwtPlot_3)
            print 'hello'
#
if __name__ == "__main__":
    import sys
    app = QtGui.QApplication(sys.argv)
    MainWindow = QtGui.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(app.exec_())

import numpy as np
from PyQt4 import QtCore, QtGui
import PyQt4.Qwt5 as Qwt
import sys, os, csv
from PyQt4.QtCore import *
from PyQt4.QtGui import *
import random


try:
    _fromUtf8 = QtCore.QString.fromUtf8
except AttributeError:
    def _fromUtf8(s):
        return s

try:
    _encoding = QtGui.QApplication.UnicodeUTF8
    def _translate(context, text, disambig):
        return QtGui.QApplication.translate(context, text, disambig, _encoding)
except AttributeError:
    def _translate(context, text, disambig):
        return QtGui.QApplication.translate(context, text, disambig)

class Ui_MainWindow(QtGui.QMainWindow):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName(_fromUtf8("MainWindow"))
        MainWindow.resize(800, 663)
        self.centralwidget = QtGui.QWidget(MainWindow)
        self.centralwidget.setObjectName(_fromUtf8("centralwidget"))
        
        

        self.pushButton_1 = QtGui.QPushButton(self.centralwidget)
        self.pushButton_1.setGeometry(QtCore.QRect(60, 20, 311, 27))
        self.pushButton_1.setObjectName(_fromUtf8("pushButton_1"))
        self.pushButton_2 = QtGui.QPushButton(self.centralwidget)
        self.pushButton_2.setGeometry(QtCore.QRect(60, 70, 311, 27))
        self.pushButton_2.setObjectName(_fromUtf8("pushButton_2"))
        
        
        
        self.qwtPlot_2 = Qwt.QwtPlot(self.centralwidget)
        self.qwtPlot_2.setGeometry(QtCore.QRect(60, 170, 400, 200))
        self.qwtPlot_2.setObjectName(_fromUtf8("qwtPlot_2"))
        self.qwtPlot_2.setAxisTitle(Qwt.QwtPlot.xBottom, 'x -->')
        self.qwtPlot_2.setAxisTitle(Qwt.QwtPlot.yLeft, 'y -->')
        grid = Qwt.QwtPlotGrid()
        pen = QPen(Qt.DotLine)
        pen.setColor(Qt.black)
        pen.setWidth(0)
        grid.setPen(pen)
        grid.attach(self.qwtPlot_2)
        
        self.qwtPlot_3 = Qwt.QwtPlot(self.centralwidget)
        self.qwtPlot_3.setGeometry(QtCore.QRect(60, 390, 400, 200))
        self.qwtPlot_3.setObjectName(_fromUtf8("qwtPlot_3"))
        self.qwtPlot_3.setAxisTitle(Qwt.QwtPlot.xBottom, 'x -->')
        self.qwtPlot_3.setAxisTitle(Qwt.QwtPlot.yLeft, 'y -->') 
        grid = Qwt.QwtPlotGrid()
        pen = QPen(Qt.DotLine)
        pen.setColor(Qt.black)
        pen.setWidth(0)
        grid.setPen(pen)
        grid.attach(self.qwtPlot_3)
        
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtGui.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 800, 25))
        self.menubar.setObjectName(_fromUtf8("menubar"))
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtGui.QStatusBar(MainWindow)
        self.statusbar.setObjectName(_fromUtf8("statusbar"))
        MainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)
        
        
        self.centralwidget.connect(self.pushButton_1, QtCore.SIGNAL('clicked()'), self.showDialog)    
        
        
           
    def retranslateUi(self, MainWindow):
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow", None))
        self.pushButton_1.setText(_translate("MainWindow", "Selec file txt", None))
        self.pushButton_2.setText(_translate("MainWindow", "Plot", None))
     
    #------------------------------------------------------------------------
              #azione apertura file0
    #------------------------------------------------------------------------              
    def showDialog(self):
           fname = QtGui.QFileDialog.getOpenFileName(self, 'Open a data file', '.', 'txt files (*.txt);;All Files (*.*)')
           f = open(fname, 'r')
           with f:
            data = np.genfromtxt(f, skiprows=1)
            self.tdata = data[:,0]
            self.cdata = data[:,1]
            curve=Qwt.QwtPlotCurve('ciao')
            curve.setData(range(len(self.tdata)), self.tdata)
            curve.attach(self.qwtPlot_3)
            print 'hello'
#
if __name__ == "__main__":
    import sys
    app = QtGui.QApplication(sys.argv)
    MainWindow = QtGui.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(app.exec_())

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Thanks in advance to all

Dear all,
I have understood why:

I have missed the replot-one:

Qt Code:

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curve = Qwt.QwtPlotCurve('Q')
        curve.attach(self.qwtPlot_2)
        curve.setPen(Qt.QPen(Qt.Qt.blue, 2))
        curve.setData(self.tdata, self.cdata)
        self.qwtPlot_2.replot()

curve = Qwt.QwtPlotCurve('Q')
        curve.attach(self.qwtPlot_2)
        curve.setPen(Qt.QPen(Qt.Qt.blue, 2))
        curve.setData(self.tdata, self.cdata)
        self.qwtPlot_2.replot()

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thanks to all and sorry for your time