This is my code:

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-- coding: utf-8 --

Form implementation generated from reading ui file 'form_2.ui'

Created: Fri Aug 1 19:49:00 2014

by: PyQt4 UI code generator 4.10.4

WARNING! All changes made in this file will be lost!

import numpy as np
from PyQt4 import QtCore, QtGui
from guiqwt.plot import CurveWidget,PlotManager
from guiqwt.plot import CurveDialog
from guiqwt.builder import make
from guiqwt.signals import SIG_CLICK_EVENT
from guiqwt.events import ClickHandler

from guidata.configtools import get_icon

import sys

from random import random

from PyQt4 import QtGui, QtCore

from PyQt4 import Qwt5

from guiqwt.plot import CurvePlot
from guiqwt.curve import CurveItem
from guiqwt.builder import make
from guiqwt.styles import CurveParam

from guiqwt.plot import CurveDialog

from guiqwt.styles import COLORS

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(object):
def setupUi(self, MainWindow):
MainWindow.setObjectName(_fromUtf8("MainWindow"))
MainWindow.resize(817, 882)
MainWindow.setMouseTracking(True)
self.centralwidget = QtGui.QWidget(MainWindow)
self.centralwidget.setObjectName(_fromUtf8("centralwidget"))
self.curvewidget = CurveWidget(self.centralwidget)
self.curvewidget.setGeometry(QtCore.QRect(80, 470, 400, 300))
self.curvewidget.setMouseTracking(True)
self.curvewidget.setOrientation(QtCore.Qt.Horizontal)
self.curvewidget.setObjectName(_fromUtf8("curvewidget"))

    range = make.range(30, 100)
    self.curvewidget.plot.add_item(range)     
    
    
    
    self.curvewidget_2 = CurveWidget(self.centralwidget)
    self.curvewidget_2.setEnabled(True)
    self.curvewidget_2.setGeometry(QtCore.QRect(80, 130, 401, 300))
    self.curvewidget_2.setMouseTracking(True)
    self.curvewidget_2.setAcceptDrops(False)
    self.curvewidget_2.setOrientation(QtCore.Qt.Horizontal)
    self.curvewidget_2.setObjectName(_fromUtf8("curvewidget_2"))
    self.pushButton = QtGui.QPushButton(self.centralwidget)
    self.pushButton.setGeometry(QtCore.QRect(130, 40, 351, 27))
    self.pushButton.setObjectName(_fromUtf8("pushButton"))
    self.frame = QtGui.QFrame(self.centralwidget)
    self.frame.setGeometry(QtCore.QRect(530, 130, 251, 281))
    self.frame.setFrameShape(QtGui.QFrame.StyledPanel)
    self.frame.setFrameShadow(QtGui.QFrame.Raised)
    self.frame.setObjectName(_fromUtf8("frame"))
    
    MainWindow.connect(self.pushButton, QtCore.SIGNAL('clicked()'), self.showDialog)         
    
    
    self.label = QtGui.QLabel(self.frame)
    self.label.setGeometry(QtCore.QRect(20, 30, 71, 17))
    self.label.setObjectName(_fromUtf8("label"))
    MainWindow.setCentralWidget(self.centralwidget)
    self.menubar = QtGui.QMenuBar(MainWindow)
    self.menubar.setGeometry(QtCore.QRect(0, 0, 817, 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)

def retranslateUi(self, MainWindow):
    MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow", None))
    self.pushButton.setText(_translate("MainWindow", "PushButton", None))
    self.label.setText(_translate("MainWindow", "portata Q", None))
    
#------------------------------------------------------------------------
          #azione apertura file
#------------------------------------------------------------------------              
def showDialog(self):
    fname = QtGui.QFileDialog.getOpenFileName(MainWindow, 'Open a data file', '.', 'txt files (*.txt);;All Files (*.*)')
    f = open(fname, 'r')
    with f:
        data = np.genfromtxt(f, skiprows=1)

self.textEdit.setText(data)

        A=-0.198058
        B=-1.992186
        C=231.17628
        D=86.39123
        alfa=0.962144
        n=0.965078
        m=1.116
        self.tdata = data[:,0]
        odata = data[:,1]
        pdata = data[:,2]
        #correzione in temperatura da norma UNI EN 27888

condc = ((1-alfa+alfa*(A+np.exp(B+C/(D+pdata)))**n)modata)

self.cdata = condc*TDS

        self.curve_item = make.curve([], [], color='b')
        self.curvewidget_2.plot.add_item(self.curve_item)
        self.curve_item.set_data(self.tdata, odata)
        self.curve_item.plot().replot()
        
        win=CurveDialog(edit=False, toolbar=True)
        self.curvewidget.plot=win.get_plot()                        
        self.curve_item.plot().replot()   

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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