# ！/usr/bin/env/ python3# -*- coding: utf-8 -*-"""用戶輸入計(jì)算表達(dá)式，顯示計(jì)算結(jié)果"""__author__ = 'Jack'import rebracket = re.compile(r'/([^()]+/)') # 尋找最內(nèi)層括號(hào)規(guī)則mul = re.compile(r'(/d+/.?/d*/*-/d+/.?/d*)|(/d+/.?/d*/*/d+/.?/d*)') # 尋找乘法運(yùn)算規(guī)則div = re.compile(r'(/d+/.?/d*/-/d+/.?/d*)|(/d+/.?/d*//d+/.?/d*)') # 尋找除法運(yùn)算規(guī)則add = re.compile(r'(-?/d+/.?/d*/+-/d+/.?/d*)|(-?/d+/.?/d*/+/d+/.?/d*)') # 尋找加法運(yùn)算規(guī)則sub = re.compile(r'(/d+/.?/d*--/d+/.?/d*)|(/d+/.?/d*-/d+/.?/d*)') # 尋找減法運(yùn)算規(guī)則c_f = re.compile(r'/(?/+?-?/d+/)?') # 檢查括號(hào)內(nèi)是否運(yùn)算完畢規(guī)則strip = re.compile(r'[^(].*[^)]') # 脫括號(hào)規(guī)則def Mul(s): """計(jì)算表達(dá)式中的乘法運(yùn)算""" exp = re.split(r'/*', mul.search(s).group()) return s.replace(mul.search(s).group(), str(float(exp[0]) * float(exp[1])))def Div(s): """計(jì)算表達(dá)式中的除法運(yùn)算""" exp = re.split(r'/', div.search(s).group()) return s.replace(div.search(s).group(), str(float(exp[0]) / float(exp[1])))def Add(s): """計(jì)算表達(dá)式中的加法運(yùn)算""" exp = re.split(r'/+', add.search(s).group()) return s.replace(add.search(s).group(), str(float(exp[0]) + float(exp[1])))def Sub(s): """計(jì)算表達(dá)式中的減法運(yùn)算""" exp = re.split(r'-', sub.search(s).group()) return s.replace(sub.search(s).group(), str(float(exp[0]) - float(exp[1])))def calc(): while True:  s = input('Please input the expression(q for quit):') # 例：'1+2- (3* 4-3/2+ ( 3-2*(3+ 5 -3* -0.2-3.3*2.2 -8.5/ 2.4 )+10) +10)'  if s == 'q':   break  else:   s = ''.join([x for x in re.split('/s+', s)]) # 將表達(dá)式按空格分割并重組   if not s.startswith('('): # 若用戶輸入的表達(dá)式首尾無(wú)括號(hào)，則統(tǒng)一格式化為：(表達(dá)式)    s = str('(%s)' % s)   while bracket.search(s): # 若表達(dá)式s存在括號(hào)    s = s.replace('--', '+') # 檢查表達(dá)式，并將--運(yùn)算替換為+運(yùn)算    s_search = bracket.search(s).group() # 將最內(nèi)層括號(hào)及其內(nèi)容賦給變量s_search    if div.search(s_search): # 若除法運(yùn)算存在(必須放在乘法之前）     s = s.replace(s_search, Div(s_search)) # 執(zhí)行除法運(yùn)算并將結(jié)果替換原表達(dá)式    elif mul.search(s_search): # 若乘法運(yùn)算存在     s = s.replace(s_search, Mul(s_search)) # 執(zhí)行乘法運(yùn)算并將結(jié)果替換原表達(dá)式    elif sub.search(s_search): # 若減法運(yùn)算存在（必須放在加法之前）     s = s.replace(s_search, Sub(s_search)) # 執(zhí)行減法運(yùn)算并將結(jié)果替換原表達(dá)式    elif add.search(s_search): # 若加法運(yùn)算存在     s = s.replace(s_search, Add(s_search)) # 執(zhí)行加法運(yùn)算并將結(jié)果替換原表達(dá)式    elif c_f.search(s_search): # 若括號(hào)內(nèi)無(wú)任何運(yùn)算（類似（-2.32）除外）     s = s.replace(s_search, strip.search(s_search).group()) # 將括號(hào)脫掉，例：（-2.32）---> -2.32   print('The answer is: %.2f' % (float(s)))if __name__ == '__main__': calc()