项目托管平台地址：https://gitee.com/Marly/codes/vbnfqyx3mzpsk8062rc9e77
fun功能,实现了不含括号的表达式计算 实现的过程：

def fun(s):
l = re.findall('([\d\.]+|/|-|\+|\*)',s)
sum=0
while 1:
if '*' in l and '/' not in l:
md(l, '*')
elif '*' not in l and '/' in l:
md(l, '/')
elif '*' in l and '/' in l:
a = l.index('*')
b = l.index('/')
if a < b:
md(l, '*')
else:
md(l, '/')
else:
if l[0]=='-':
l[0]=l[0]+l[1]
del l[1]
sum += float(l[0])
for i in range(1, len(l), 2):
if l[i] == '+' and l[i + 1] != '-':
sum += float(l[i + 1])
elif l[i] == '+' and l[i + 1] == '-':
sum -= float(l[i + 2])
elif l[i] == '-' and l[i + 1] == '-':
sum += float(l[i + 2])
elif l[i] == '-' and l[i + 1] != '-':
sum -= float(l[i + 1])
break
return sum

calculate功能,:实现了带有括号的递归运算。实现过程是

def calculate(expression):
ex=[]
ans=0
if '(' not in expression:
ans=fun(expression)
return ans
for i in range(len(expression)):
if expression[i]=='(':
ex.append(i)
elif expression[i]==')':
temp=0
sub=expression[ex[len(ex)-1]+1:i]
temp=fun(sub)
expression=expression[0:ex[len(ex)-1]]+str(temp)+expression[i+1:len(expression)+1]
ex.pop()