解析四则算式并计算

from re import sub as replacefrom re import search as findfrom re import split'''***********解析四则算式并计算***********''''''全局正则定义'''#乘除正则，查找乘除操作mul_div_calc_regex =  r'\d+(\.\d+)?[\*\/]\d+(\.\d+)?'#加减正则，查找加减操作plus_sub_calc_regex =  r'\d+(\.\d+)?[\+\-]\d+(\.\d+)?'#括号正则，查找括号运算mark_regex = r'\([^\(]*?\)'#运算正则，查找具体操作calc_regex = r'[\+\-\*\/]'def basic_calc(a,mark, b):    '''简单计算'''    a = float(a)    b = float(b)    ans = 0    if mark == '*':        ans = a*b    elif mark == '/':        ans = a/b    elif mark == '+':        ans = a+b    elif mark == '-':        ans = a-b    return ansdef calc_by_string(s):    '''字符串拆分计算'''    global calc_regex    a = split(calc_regex,s)    mark = find(calc_regex,s).group()    return basic_calc(a[0],mark, a[1])def mul_div(s):    '''查找字符串中加减操作，并计算'''    global mul_div_calc_regex    while find(mul_div_calc_regex, s):        a = find(mul_div_calc_regex, s).group()        ans = calc_by_string(a)        s = replace(mul_div_calc_regex, str(ans), s,count=1)    return sdef plus_sub(s):    '''查找字符串中乘除操作，并计算'''    global plus_sub_calc_regex    while find(plus_sub_calc_regex, s):        a = find(plus_sub_calc_regex, s).group()        ans = calc_by_string(a)        s = replace(plus_sub_calc_regex, str(ans), s,count=1)    return sdef calc_one(s):    '''计算一个简单等式，不包含括号'''    return plus_sub(mul_div(s))def mark_calc(s):    '''查找括号，并计算'''    global mark_regex    while find(mark_regex,s):        print(s)        a = find(mark_regex, s).group()        ans = calc_one(replace(r'[\(\)]','',a))        s = replace(mark_regex,ans,s,count=1)    print(s)    return sdef calc_all(s):    '''全部计算'''    return plus_sub(mul_div(mark_calc(s)))test_string = '1+(9+(32*1)+(25/5)-3)*(3*9-5+3)'print(calc_all(test_string))

计算过程显示如下

1+(9+(32*1)+(25/5)-3)*(3*9-5+3)1+(9+32.0+(25/5)-3)*(3*9-5+3)1+(9+32.0+5.0-3)*(3*9-5+3)1+43.0*(3*9-5+3)1+43.0*25.01076.0