| wps2000 |
2016-10-11 13:35 |
解决第4章例子“30行的表达式求值”对PyQt5+Python3兼容性的问题。
原来书中的代码是这样的：
from __future__ import division
import sys
from math import *
from PyQt4.QtCore import *
from PyQt4.QtGui 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 = unicode(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_()
第一，对于PyQt5来说，还是老问题，要把from PyQt5.QtWidgets import *加进去。
第二，类Form，是QDialog的子类，在Form类中，
self.connect(self.lineedit, SIGNAL("returnPressed()"),
self.updateUi)
里面的connect在 PyQt5中已经取消。如果运行的话，会出现：AttributeError: 'Form' object has no attribute 'connect'，这个错误。要改成：
self.lineedit.returnPressed.connect(self.updateUi)
因此，完整的代码为：
from __future__ import division
import sys
from math import *
from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.QtWidgets 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.lineedit.returnPressed.connect(self.updateUi)
self.setWindowTitle("Calculate")
def updateUi(self):
try:
text = unicode(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_()
但最后一个问题，始终没解决。那就是对话框出来之后，输入数学表达式，对话框就自动消失了。换成PyQt4也很扯，虽然没消失，但对话框没任何反应。请高手指教。
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