Python function to determine whether it is a decimal

Demand analysis: 
1. Number of decimal points. count() 
2. Divide according to the decimal point 1.98 [1,98] 
3. Positive decimal: the left side of the decimal point is an integer, and the right side is also an integer. isdigits() Negative decimal: the left side of the decimal point is a negative sign At the beginning, but there is only one negative sign, and the right side is also an integer. The 
code is as follows:

1  def is_fioat(s):
 2      s= str(s)
 3      if s.count( " . " )==1: #Number of decimal points 
4          s_list=s. split( " . " )
 5          left = s_list[0] # 6 to the left of the decimal point
          right =s_list[1] # 7 to the right of the decimal point if left.isdigit() and right.isdigit():
 8 return   True
 9 elif left.startswith( ' - ' ) and left.count(
                               '_')==1 and left.split('-')[1].isdigit()and right.isdigit():
10             return  True
11     return  False