计算加减乘除混合运算python实现_python,实现计算器程序,加减乘除混合运算加括号,完善实现...
作业:要求实现一个由键盘输入表达式,计算结果的小程序.
import re
#detect error input
s = input("Expression:")
s = re.sub('\s',"",s)
if re.findall('[^0-9\+\-\*/\)\(]',s):
print("Error input,Stop!")
exit()
def judge1(sign):
if sign == '*':
obj = re.compile('\*')
elif sign == '/':
obj = re.compile('/')
return(obj)
def judge2(sign):
if sign == '+':
obj = re.compile('\+')
elif sign == '-':
obj = re.compile('\-')
return(obj)
def Format(s):
s = s.replace(' ','')
s = s.replace('++','+')
s = s.replace('+-','-')
s = s.replace('-+','-')
s = s.replace('--','+')
return(s)
def calculate(s):
while re.search('[\*,/]',s):
s = Format(s)
obj = judge1(re.search('[\*,/]',s).group())
res = obj.split(s)
first = re.search('[\d,\.]+$',res[0]).group()
second = re.search('^[\d,\.,\-]+',res[1]).group()
if re.search('\.',first):
fir = float(first)
else:
fir = int(first)
if re.search('\.',second):
sec = float(second)
else:
sec = int(second)
if re.search('[\*,/]',s).group() == '*':
result = str((fir * sec))
s = re.sub('%s\*%s'%(first,second),result,s)
print('s=',s)
elif re.search('[\*,/]',s).group() == '/':
result = str(fir / sec)
s = re.sub('%s/%s'%(first,second),result,s)
print('s=',s)
if re.search('^\-[\d,\.]+',s):
return(s)
s = Format(s)
# return(s)
while re.search('[\+,\-]',s):
s = Format(s)
obj = judge2(re.search('[\+,\-]',s).group())
res = obj.split(s)
first = re.search('[\d,\.]+$',res[0]).group()
second = re.search('^[\d,\.,\-]+',res[1]).group()
if re.search('\.',first):
fir = float(first)
else:
fir = int(first)
if re.search('\.',second):
sec = float(second)
else:
sec = int(second)
if re.search('[\+,\-]',s).group() == '+':
result = str(fir + sec)
s = re.sub('%s\+*%s'%(first,second),result,s)
print('s=',s)
elif re.search('[\+,\-]',s).group() == '-':
result = str(fir - sec)
s = re.sub('%s\-%s'%(first,second),result,s)
print('=',s)
if re.search('^\-[\d,\.]+',s):
return(s)
s= Format(s)
return(s)
def first_step(s):
while re.search('\([^()]+\)',s):
res = re.search('\([^()]+\)',s)
s_temp = res.group()
print(s_temp)
[first,second] = s.split(s_temp)
ret = re.search('\([^()]+\)',s)
tmp = re.search('[^()]+',ret.group())
print(tmp.group())
temp = str(calculate(tmp.group()))
print('temp=',temp)
s = first + temp + second
print('first=',first)
print('second=',second)
print('temp=',temp)
print('new s=',s)
# if re.search('[\+,\-]{1}',s):
# break
result = calculate(s)
print("result=",result)
first_step(s)
花了两天时间终于完成这个小作业了,其实没什么难度,就是正则表达式的灵活运用,由于逻辑比较复杂,测试花费了很多时间.
标签：search,group,python,re,second,计算器,print,加减乘除,first
来源： https://www.cnblogs.com/iceberg710815/p/11965177.html