不完善：1.若是公式里没（）ui
2.算到中间部，可能有*-， +- ，-- ，这样的状况spa
import re '''计算字符串表达式''' bracket = re.compile('\([^()]+\)') # 查找最内层括号 div = re.compile('(\d+\.?\d*/-\d+\.?\d*)|(\d+\.?\d*/\d+\.?\d*)') # 查找除法运算 mul = re.compile('(\d+\.?\d*\*-\d+\.?\d*)|(\d+\.?\d*\*\d+\.?\d*)') # 查找乘法运算 add = re.compile('(-\d+\.?\d*\+\d+\.?\d*)|(\d+\.?\d*\+\d+\.?\d*)') # 查找加法运算 sub = re.compile('(-\d+\.?\d*-\d+\.?\d*)|(\d+\.?\d*-\d+\.?\d*)') # 查找减法运算 c_f=re.compile('\(?\d+\)?') strip=re.compile('[^()]') def Div(s): exp = re.split('/', div.search(s).group()) return s.replace(div.search(s).group(), str(float(exp[0]) / float(exp[1]))) def Mul(s): exp = re.split('\*', mul.search(s).group()) return s.replace(mul.search(s).group(), str(float(exp[0]) * float(exp[1]))) def Add(s): exp = re.split('\+', add.search(s).group()) return s.replace(add.search(s).group(), str(float(exp[0]) + float(exp[1]))) def Sub(s): exp = sub.search(s).group() if exp.startswith('-'): exp = exp.replace('-', '+') exp = exp.replace('+', '', 1) res = Add(exp) return s.replace(sub.search(s).group(), '-' + res) else: exp = re.split('-', sub.search(s).group()) return s.replace(sub.search(s).group(), str(float(exp[0]) - float(exp[1]))) def calc(): while True: s = input('请输入等式').replace(' ','') if s=='quit': break else: while bracket.search(s): s_search=bracket.search(s).group() if div.search(s_search): s=s.replace(s_search,Div(s_search)) elif mul.search(s_search): s=s.replace(s_search,Mul(s_search)) elif sub.search(s_search): s = s.replace(s_search, Sub(s_search)) elif add.search(s_search): s=s.replace(s_search,Add(s_search)) elif c_f.search(s_search): s=s.replace(s_search,strip.search(s_search).group()) print(s) calc()