3 Python Lab Calculator: Subtraction

#--time:2017/12/31 1:25
#--file:day18 Calculator job. py
#__author: "CFP"
#date: 2017/12/30
Import re
Source= ' 1+ (2*2)/11+3++ (2+-2) +2 '


# #判断子串是否合法
def check_string (source):
Flat = True
If Re.search (' [a-za-z] ', source):
Print ("Invalid illegal characters! ")
Flat = False
If Source.count ("(")! = Source.count (")"):
Print ("Expression error, parenthesis not closed! ")
Flat = False
return flat

# #将子串格式化
def format_string (source):
Source = Source.replace ("", "")
Source = Source.replace ("+ +", "+")
Source = Source.replace ("-+", "-")
Source = Source.replace ("+-", "-")
Source = Source.replace ("/+", "/")
Source = Source.replace ("*+", "*")
return source

# #乘除法函数, pass in one () content at a time
def calc_mul_div (String):
Mul_regular = ' \d+\.? \d*\*\d+\.? \d* ' # #乘法匹配模式去掉 ()
Div_regular = ' \d+\.? \d*\/\d+\.? \d* ' # #乘法匹配模式去掉 ()

# #循环进入条件, when () this string has an * number
While Re.findall (' \* ', string):

# #一次匹配一组args * args data
expression = Re.search (mul_regular,string). Group ()

# #计算args * Args This set of data
I,v = Expression.split (' * ')
Mul_result = str (float (i) *float (v))

# #将计算后的一组args * args data; replace args * args
String = String.Replace (Expression,mul_result)

# # #将子串在进行格式化下
String = String.Format (String)

While Re.findall (' \ \ ', string):
expression = Re.search (div_regular,string). Group ()
I,v = Expression.split ('/')
Div_result = str (float (i)/float (v))
String = String.Replace (Expression,div_result)
String = String.Format (String)
return string

# #加减法函数, pass in one () content at a time
def calc_add_sub (String):
Add_sub_regular = ' \d+\.? \d*\+\d+\.? \d* '
Add_sub1_regular = ' \d+\.? \d*\-\d+\.? \d* '
While Re.findall (' \+ ', string):
expression = Re.search (add_sub_regular,string). Group ()
I,v = expression.split (' + ')
Add_result = str (float (i) +float (v))
String=string.replace (Expression,add_result)
String = format_string (String)
While Re.findall (' \-', string):
expression1 = Re.search (Add_sub1_regular, String)
Try
Expression1=expression1.group ()
Except Attributeerror:
Break
I,v = Expression1.split ("-")
Sub_result = str (float (i)-float (v))
String=string.replace (Expression1,sub_result)
String=format_string (String)
return string

# #子串通过检查函数进入if语句
If check_string (source):
Print ("Souece:", source)
Source = format_string (source)
Print ("Format:", source)

# #打印子串通过eval得到数据用于验证, the results of the code are consistent
Print (' eval: ', eval (source))

# #当子串有 () into the loop until there is no (); Execute Else statement
While Re.search (' \ (', source):

# #匹配最深处的 () data and pass it to the subtraction function to resolve () data
Strs_regular = ' \ ([^ ()]+\) '
STRs = Re.search (strs_regular,source). Group ()
Strs_result = Calc_mul_div (STRs)
Strs_result = Calc_add_sub (Strs_result)

# #将 () Remove both sides (and), leaving only the contents, and replace the original ()
Strs_result = Strs_result[1:-1]
Source=source.replace (Strs,strs_result)
Source = format_string (source)
Else
Strs_result = Calc_mul_div (source)
Strs_result = Calc_add_sub (Strs_result)
Source=source.replace (Source,strs_result)
Source = format_string (source)

Print ("calculator:", source)

3 Python Lab Calculator: Subtraction