python determines whether a string of decimal

"" " 
Exercise to determine a decimal 
1, to determine the legality of 
2, the legitimate need for a decimal point 
3, to the left of the decimal point must be an integer, the right must be a positive integer 

" "" 

DEF Xiaoshu (S): 
    xiaoshu_new = str (S) 

    IF xiaoshu_new. COUNT ( ".") ==. 1: 
       left, right = xiaoshu_new.split ( ".") 
       IF left.isdigit () and right.isdigit (): 
           Print (1111) 
           return True 

       elif left.startswith ( '-') left.count and ( '-'). 1 and right.isdigit == (): 
            lleft left.split = ( '-') [-. 1] 
            IF lleft.isdigit (): 
                return True 

    return False 


A Xiaoshu = (-. . 1) 

Print (A)