刚开始只是为了实现某个功能，中间需要对表达式进行计算，想着写个四则运算计算器也很简单就顺手写了， 写到后面发现需要考虑的问题还挺多的，囧。
现在把代码贴出来记录一下这辛苦的过程吧，毕竟写得挺长的= =
不做解释了，单纯为了记录，毕竟写的也挺菜的，也就能基本实现功能2333
def calculate(in_formula: str) -> int:
"""
对字符串类型的数学表达式进行计算，返回计算结果
数学表达式可包含加减乘除、括号
:param in_formula: 数学表达式 如'2*(-5+3)/-1+20/(3+1)+2+(-9-2)*2'
:return: 计算结果
"""
if '(' in in_formula:
result_in_brackets = []
reg_formula_in_brackets = re.compile(r'([^(]+)')
formula_in_brackets = reg_formula_in_brackets.findall(in_formula)
else_formula = reg_formula_in_brackets.split(in_formula)
for i in formula_in_brackets:
result_in_brackets.append(simple_arithmetic(re.sub(r"[()]", '', i)))
for i in range(0, int(len(else_formula)) + 1, 2):
else_formula.insert(i + 1, str(result_in_brackets[int(i / 2)]))
result = simple_arithmetic(''.join(else_formula))
else:
result = simple_arithmetic(''.join(in_formula))
return result
def simple_arithmetic(in_formula: str) -> int:
"""
不含括号的简单公式计算（加减乘除）
:param in_formula: 只包含加减乘除不含括号的计算公式
:return: 计算结果
"""
result = 0
if '+' in in_formula or '-' in in_formula:
reg = re.compile(r"(?<![+*/-])[+-]")
operators = reg.findall(in_formula)
sub_formulas = reg.split(in_formula)
for ind, sub_formula in enumerate(sub_formulas):
if ind == 0 and sub_formula == '':
sub_formulas[0] = 0
sub_formulas[1] = operators[0] + sub_formulas[1]
operators[0] = '+'
continue
if '/' in sub_formula or '*' in sub_formula:
val = multiply_divide(sub_formula)
else:
val = int(sub_formula)
sub_formulas[ind] = val
result = sub_formulas[0]
for ind, i in enumerate(operators):
if i == '+':
result += int(sub_formulas[ind + 1])
elif i == '-':
result -= int(sub_formulas[ind + 1])
elif '/' in in_formula or '*' in in_formula:
result = multiply_divide(in_formula)
else:
return result
return result
def multiply_divide(in_formula: str) -> int:
"""
乘除法的计算
:param in_formula:只含有乘除法的计算公式
:return: 计算结果
"""
result = 1
if '/' not in in_formula:
sub_formulas = in_formula.split('*')
for i in sub_formulas:
result = result * int(i)
elif '*' not in in_formula:
sub_formulas = in_formula.split('/')
for ind, i in enumerate(sub_formulas):
result = int(i) if ind == 0 else result / int(i)
else:
reg = re.compile(r'[*/]')
operators = reg.findall(in_formula)
sub_formulas = reg.split(in_formula)
result = int(sub_formulas[0])
for ind, i in enumerate(operators):
if i == '*':
result = int(sub_formulas[ind + 1]) * result
elif i == '/':
result = result / int(sub_formulas[ind + 1])
return result
def addition_subtraction(formula: str) -> int:
"""
加减法运算
:param formula:只含有加减法的运算公式
:return: 运算结果
"""
result = 0
if '+' not in formula:
sub_formulas = formula.split('-')
result = int(sub_formulas[0])
for i in sub_formulas[1:]:
result = result - int(i)
elif '-' not in formula:
sub_formulas = formula.split('+')
for i in sub_formulas:
result = int(i) + result
elif '+' in formula or '-' in formula:
reg = re.compile(r'[+-]')
operators = reg.findall(formula)
sub_formulas = reg.split(formula)
result = int(sub_formulas[0])
for ind, i in enumerate(operators):
if i == '+':
result += int(sub_formulas[ind + 1])
elif i == '-':
result -= int(sub_formulas[ind + 1])
else:
return formula
return result
if __name__ == '__main__':
print(calculate('2*(-5+3)/-1+20/(3+1)+2+(-9-2)*2'))