import sys

from PySide.QtCore import *

from PySide.QtGui import *

from math import *

class Form(QDialog):

def __init__(self, parent=None):

super(Form, self).__init__(parent)

self.browser = QTextBrowser()

self.lineedit = QLineEdit("Type an expression and press Enter")

self.lineedit.selectAll()

layout = QVBoxLayout()

layout.addWidget(self.browser)

layout.addWidget(self.lineedit)

self.setLayout(layout)

self.lineedit.setFocus()

self.connect(self.lineedit, SIGNAL("returnPressed()"), self.updateUi)

self.setWindowTitle("Calculate")

def updateUi(self):

try:

text = self.lineedit.text()

self.browser.append("%s = <b>%s</b>" % (text, eval(text)))

except:

self.browser.append("<font color=red>%s is invalid</font>" % text)

app = QApplication(sys.argv)

form = Form()

form.show()

app.exec_()