目前可以实现简单的计算。计算前请重置，设计的时候默认数字是0，学了半天就做出来个这么个结果，bug不少。 python3.5 + PyQt5 +Eric6 在windows7 32位系统可以完美运行 计算器，简单学了半天就画个图实现的存在bug，部分按钮还未实现，后续优化。

代码结构如图：

jisuan.py

import re
#匹配整数或小数的乘除法，包括了开头存在减号的情况
mul_p=re.compile("(-?d+)(.d+)?(*|/)(-?d+)(.d+)?")
#匹配整数或小数的加减法，包括了开头存在减号的情况
plus_minus = re.compile("(-?d+)(.d+)?(-|+)(-?d+)(.d+)?")
#匹配括号
bracket=re.compile("([^()]*)")
#匹配乘法的时候出现乘以负数的情况，包括了开头存在减号的情况
mul_minus_minus = re.compile("(-?d+)(.d+)?(*-)(d+)(.d+)?")
#匹配除法的时候出现乘以负数的情况，包括了开头存在减号的情况
p_minus_minus = re.compile("(-?d+)(.d+)?(/-)(d+)(.d+)?")
#定义一个两位数的加减乘除法的运算，匹配左边的右边的数字和左边的数字，然后进行计算
def touble_cale(str_expire):
 if str_expire.count("+") == 1:
 right_num = float(str_expire[(str_expire.find("+")+1):])
 left_num = float(str_expire[:str_expire.find("+")])
 return str(right_num+left_num)
 elif str_expire[1:].count("-") == 1:
 right_num = float(str_expire[:str_expire.find("-",1)])
 left_num = float(str_expire[(str_expire.find("-", 1) + 1):])
 return str(right_num - left_num)
 elif str_expire.count("*") == 1:
 right_num = float(str_expire[:str_expire.find("*")])
 left_num = float(str_expire[(str_expire.find("*")+1):])
 return str(right_num * left_num)
 elif str_expire.count("/") == 1:
 right_num = float(str_expire[:str_expire.find("/")])
 left_num = float(str_expire[(str_expire.find("/") + 1):])
 return str(right_num / left_num)


#定义一个方法用于判断是否存在乘以负数和除以负数的情况
def judge_mul_minus(str_expire):
 #判断公式中乘以负数的部分
 if len(re.findall("(*-)", str_expire)) != 0:
 #调用上面的正则取得*-的公式
 temp_mul_minus = mul_minus_minus.search(str_expire).group()
 #将匹配的部分的*-换成*并将-放到前面
 temp_mul_minus_2 = temp_mul_minus.replace(temp_mul_minus,"-" + temp_mul_minus.replace("*-","*"))
 #经更改的的部分与原来的部分进行替换
 str_expire=str_expire.replace(temp_mul_minus,temp_mul_minus_2)
 return judge_mul_minus(str_expire)
 #return str_expire
 # 判断公式中除以负数的部分
 elif len(re.findall(r"(/-)", str_expire)) != 0:
 # 调用上面的正则取得/-的公式
 temp_dev_minus = p_minus_minus.search(str_expire).group()
 # 将匹配的部分的/-换成/并将-放到前面
 temp_dev_minus_2 = temp_dev_minus.replace(temp_dev_minus,"-" + temp_dev_minus.replace("/-","/"))
 # 经更改的的部分与原来的部分进行替换
 str_expire = str_expire.replace(temp_dev_minus,temp_dev_minus_2)
 return judge_mul_minus(str_expire)
 #调用change_sign将公式中的++换成= +-换成-
 return change_sign(str_expire)

#定义一个方法取将--更改为+ +-改为-
def change_sign(str_expire):
 if len(re.findall(r"(+-)", str_expire)) != 0:
 str_expire = str_expire.replace("+-", "-")
 return change_sign(str_expire)
 elif len(re.findall(r"(--)", str_expire)) != 0:
 str_expire = str_expire.replace("--", "+")
 return change_sign(str_expire)
 return str_expire


#定义一个方法用于计算只有加减乘除的公式，优先处理乘法
def cale_mix(str_expire):
 #如果公式中出现符号数字的情况即+5 -6 *8 /8的这种情况直接放回数字否则则先计算乘除在处理加减
 while len(re.findall("[-+*/]",str_expire[1:])) != 0:
 if len(re.findall("(*|/)",str_expire)) != 0:
 str_expire = str_expire.replace(mul_p.search(str_expire).group(),touble_cale(mul_p.search(str_expire).group()))
 elif len(re.findall("(+|-)",str_expire)) !=0:
 str_expire = str_expire.replace(plus_minus.search(str_expire).group(),touble_cale(plus_minus.search(str_expire).group()))
 return str_expire

#定义一个方法用于去括号,并调用上述的方法进行计算
def remove_bracket(str_expire):
 #判断公式中是否有括号
 if len(bracket.findall(str_expire)) == 0:
 return cale_mix(judge_mul_minus(str_expire))
 elif len(bracket.findall(str_expire))!=0:
 while len(bracket.findall(str_expire)) !=0:
 #print(bracket.search(str_expire).group())
 #只有存在括号优先处理括号中的内容并对内容进行替换，直到没有括号位置
 str_expire = str_expire.replace(bracket.search(str_expire).group(),cale_mix(judge_mul_minus(bracket.search(str_expire).group()[1:-1])))
 str_expire = cale_mix(judge_mul_minus(str_expire))
 return str_expire
if name == "main":
 while True:
 user_input_expire = input("请输入你的公式:(不要带空格,q表示退出):")
 print("%s=%s" %(user_input_expire,remove_bracket(user_input_expire)))
 continue

untitled.py

# -*- coding: utf-8 -*-
from PyQt5.QtCore import *
from PyQt5.QtWidgets import *
from PyQt5 import QtCore, QtGui, QtWidgets
from Ui_untitled import Ui_Dialog
from jisuan import remove_bracket
class Dialog(QDialog, Ui_Dialog):
 def init(self, parent=None):
 super(Dialog, self).init(parent)
 self.setupUi(self)
 @pyqtSlot()
 def on_Button_6_clicked(self):
 self.Edit_xianshi.insertPlainText('6')
 @pyqtSlot()
 def on_Button_2_clicked(self):
 self.Edit_xianshi.insertPlainText('2')
 @pyqtSlot()
 def on_Button_3_clicked(self):
 self.Edit_xianshi.insertPlainText('3')
 @pyqtSlot()
 def on_Button_pingfang_clicked(self):
 me=self.Edit_xianshi.toPlainText()
 m=int(me) *int(me)
 self.Edit_xianshi.clear()
 self.Edit_xianshi.append(str(m))
 @pyqtSlot()
 def on_Button_add_clicked(self):
 h=self.Edit_xianshi.toPlainText()
 self.Edit_xianshi.clear()
 self.Edit_xianshi.append(h+'+')
 @pyqtSlot()
 def on_Button_jian_clicked(self):
 h = self.Edit_xianshi.toPlainText()
 self.Edit_xianshi.clear()
 self.Edit_xianshi.append(h + '-')
 @pyqtSlot()
 def on_Button_9_clicked(self):
 self.Edit_xianshi.insertPlainText('9')
 @pyqtSlot()
 def on_Button_chu_clicked(self):
 h = self.Edit_xianshi.toPlainText()
 self.Edit_xianshi.clear()
 self.Edit_xianshi.append(h + '/')
 @pyqtSlot()
 def on_Button_cheng_clicked(self):
 h = self.Edit_xianshi.toPlainText()
 self.Edit_xianshi.clear()
 self.Edit_xianshi.append(h + '*')
 @pyqtSlot()
 def on_Button_8_clicked(self):
 self.Edit_xianshi.insertPlainText('8')
 @pyqtSlot()
 def on_Button_4_clicked(self):
 self.Edit_xianshi.insertPlainText('4')
 @pyqtSlot()
 def on_Button_esc_clicked(self):
 self.Edit_xianshi.clear()
 @pyqtSlot()
 def on_Button_7_clicked(self):
 self.Edit_xianshi.insertPlainText('7')
 @pyqtSlot()
 def on_Button_1_clicked(self):
 self.Edit_xianshi.insertPlainText('1')
 @pyqtSlot()
 def on_Button_5_clicked(self):
 self.Edit_xianshi.insertPlainText('5')
 @pyqtSlot()
 def on_Button_xiaoshu_clicked(self):
 self.Edit_xianshi.insertPlainText('.')
 @pyqtSlot()
 def on_Button_0_clicked(self):
 self.Edit_xianshi.insertPlainText('0')
 @pyqtSlot()
 def on_Button_dengyu_clicked(self):
 pe=self.Edit_xianshi.toPlainText()
 m=remove_bracket(pe)
 self.Edit_xianshi.clear()
 self.Edit_xianshi.append(str(m))

 def on_Button_fenzhi_clicked(self):
 pe = self.Edit_xianshi.toPlainText()
 if int(pe) ==0:
 QMessageBox.information(self,u'提示',u'零不能作为分母')
 Dialog()
 else:
 m=1/(int(pe))
 self.Edit_xianshi.clear()
 self.Edit_xianshi.append(str(m))
 Dialog()
if name =="main":
 import sys
 app = QtWidgets.QApplication(sys.argv)
 app.processEvents()
 ui = Dialog()
 ui.show()

 sys.exit(app.exec_())

Ui_untitled.py

# -*- coding: utf-8 -*-

# Form implementation generated from reading ui file 'C:UsersAdministratorDesktoppyqt5untitled.ui'
#
# Created by: PyQt5 UI code generator 5.5
#
# WARNING! All changes made in this file will be lost!

from PyQt5 import QtCore, QtGui, QtWidgets

class Ui_Dialog(object):
 def setupUi(self, Dialog):
 Dialog.setObjectName("Dialog")
 Dialog.resize(357, 320)
 Dialog.setStyleSheet("font: 75 16pt "Aharoni";
"
"background-color: rgb(206, 255, 251);")
 self.label = QtWidgets.QLabel(Dialog)
 self.label.setGeometry(QtCore.QRect(201, 210, 301, 21))
 self.label.setText("")
 self.label.setObjectName("label")
 self.Edit_xianshi = QtWidgets.QTextEdit(Dialog)
 self.Edit_xianshi.setGeometry(QtCore.QRect(0, 0, 351, 41))
 self.Edit_xianshi.setStyleSheet("font: 75 16pt "Aharoni";")
 self.Edit_xianshi.setObjectName("Edit_xianshi")
 self.gridLayoutWidget = QtWidgets.QWidget(Dialog)
 self.gridLayoutWidget.setGeometry(QtCore.QRect(0, 30, 351, 281))
 self.gridLayoutWidget.setObjectName("gridLayoutWidget")
 self.gridLayout = QtWidgets.QGridLayout(self.gridLayoutWidget)
 self.gridLayout.setObjectName("gridLayout")
 self.Button_6 = QtWidgets.QPushButton(self.gridLayoutWidget)
 self.Button_6.setObjectName("Button_6")
 self.gridLayout.addWidget(self.Button_6, 2, 2, 1, 1)
 self.Button_2 = QtWidgets.QPushButton(self.gridLayoutWidget)
 self.Button_2.setObjectName("Button_2")
 self.gridLayout.addWidget(self.Button_2, 3, 1, 1, 1)
 self.Button_3 = QtWidgets.QPushButton(self.gridLayoutWidget)
 self.Button_3.setObjectName("Button_3")
 self.gridLayout.addWidget(self.Button_3, 3, 2, 1, 1)
 self.Button_fenzhi = QtWidgets.QPushButton(self.gridLayoutWidget)
 self.Button_fenzhi.setObjectName("Button_fenzhi")
 self.gridLayout.addWidget(self.Button_fenzhi, 1, 3, 1, 1)
 self.Button_pingfang = QtWidgets.QPushButton(self.gridLayoutWidget)
 self.Button_pingfang.setObjectName("Button_pingfang")
 self.gridLayout.addWidget(self.Button_pingfang, 0, 3, 1, 1)
 self.Button_add = QtWidgets.QPushButton(self.gridLayoutWidget)
 self.Button_add.setObjectName("Button_add")
 self.gridLayout.addWidget(self.Button_add, 2, 3, 1, 1)
 self.Button_jian = QtWidgets.QPushButton(self.gridLayoutWidget)
 self.Button_jian.setObjectName("Button_jian")
 self.gridLayout.addWidget(self.Button_jian, 3, 3, 1, 1)
 self.Button_9 = QtWidgets.QPushButton(self.gridLayoutWidget)
 self.Button_9.setObjectName("Button_9")
 self.gridLayout.addWidget(self.Button_9, 1, 2, 1, 1)
 self.Button_chu = QtWidgets.QPushButton(self.gridLayoutWidget)
 self.Button_chu.setObjectName("Button_chu")
 self.gridLayout.addWidget(self.Button_chu, 0, 2, 1, 1)
 self.Button_cheng = QtWidgets.QPushButton(self.gridLayoutWidget)
 self.Button_cheng.setObjectName("Button_cheng")
 self.gridLayout.addWidget(self.Button_cheng, 0, 1, 1, 1)
 self.Button_8 = QtWidgets.QPushButton(self.gridLayoutWidget)
 self.Button_8.setObjectName("Button_8")
 self.gridLayout.addWidget(self.Button_8, 1, 1, 1, 1)
 self.Button_4 = QtWidgets.QPushButton(self.gridLayoutWidget)
 self.Button_4.setObjectName("Button_4")
 self.gridLayout.addWidget(self.Button_4, 2, 0, 1, 1)
 self.Button_esc = QtWidgets.QPushButton(self.gridLayoutWidget)
 self.Button_esc.setObjectName("Button_esc")
 self.gridLayout.addWidget(self.Button_esc, 0, 0, 1, 1)
 self.Button_7 = QtWidgets.QPushButton(self.gridLayoutWidget)
 self.Button_7.setObjectName("Button_7")
 self.gridLayout.addWidget(self.Button_7, 1, 0, 1, 1)
 self.Button_1 = QtWidgets.QPushButton(self.gridLayoutWidget)
 self.Button_1.setObjectName("Button_1")
 self.gridLayout.addWidget(self.Button_1, 3, 0, 1, 1)
 self.Button_5 = QtWidgets.QPushButton(self.gridLayoutWidget)
 self.Button_5.setObjectName("Button_5")
 self.gridLayout.addWidget(self.Button_5, 2, 1, 1, 1)
 self.pushButton_17 = QtWidgets.QPushButton(self.gridLayoutWidget)
 self.pushButton_17.setText("")
 self.pushButton_17.setObjectName("pushButton_17")
 self.gridLayout.addWidget(self.pushButton_17, 4, 0, 1, 1)
 self.Button_xiaoshu = QtWidgets.QPushButton(self.gridLayoutWidget)
 self.Button_xiaoshu.setObjectName("Button_xiaoshu")
 self.gridLayout.addWidget(self.Button_xiaoshu, 4, 1, 1, 1)
 self.Button_0 = QtWidgets.QPushButton(self.gridLayoutWidget)
 self.Button_0.setStyleSheet("")
 self.Button_0.setObjectName("Button_0")
 self.gridLayout.addWidget(self.Button_0, 4, 2, 1, 1)
 self.Button_dengyu = QtWidgets.QPushButton(self.gridLayoutWidget)
 self.Button_dengyu.setObjectName("Button_dengyu")
 self.gridLayout.addWidget(self.Button_dengyu, 4, 3, 1, 1)

 self.retranslateUi(Dialog)
 QtCore.QMetaObject.connectSlotsByName(Dialog)

 def retranslateUi(self, Dialog):
 _translate = QtCore.QCoreApplication.translate
 Dialog.setWindowTitle(_translate("Dialog", "Dialog"))
 self.Edit_xianshi.setHtml(_translate("Dialog", "<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN" "http://www.w3.org/TR/REC-html40/strict.dtd">
"
"<html><head><meta name="qrichtext" content="1" /><style type="text/css">
"
"p, li { white-space: pre-wrap; }
"
"</style></head><body style=" font-family:'Aharoni'; font-size:16pt; font-weight:72; font-style:normal;">
"
"<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span style=" font-family:'SimSun'; font-weight:400;">0</span></p></body></html>"))
 self.Button_6.setText(_translate("Dialog", "6"))
 self.Button_2.setText(_translate("Dialog", "2"))
 self.Button_3.setText(_translate("Dialog", "3"))
 self.Button_fenzhi.setText(_translate("Dialog", "1/^"))
 self.Button_pingfang.setText(_translate("Dialog", "^2"))
 self.Button_add.setText(_translate("Dialog", "+"))
 self.Button_jian.setText(_translate("Dialog", "-"))
 self.Button_9.setText(_translate("Dialog", "9"))
 self.Button_chu.setText(_translate("Dialog", "/"))
 self.Button_cheng.setText(_translate("Dialog", "*"))
 self.Button_8.setText(_translate("Dialog", "8"))
 self.Button_4.setText(_translate("Dialog", "4"))
 self.Button_esc.setText(_translate("Dialog", "esc"))
 self.Button_7.setText(_translate("Dialog", "7"))
 self.Button_1.setText(_translate("Dialog", "1"))
 self.Button_5.setText(_translate("Dialog", "5"))
 self.Button_xiaoshu.setText(_translate("Dialog", "."))
 self.Button_0.setText(_translate("Dialog", "0"))
 self.Button_dengyu.setText(_translate("Dialog", "="))


if name == "main":
 import sys
 app = QtWidgets.QApplication(sys.argv)
 Dialog = QtWidgets.QDialog()
 ui = Ui_Dialog()
 ui.setupUi(Dialog)
 Dialog.show()
 sys.exit(app.exec_())

效果图：

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