def isfloat(value):
    """   
    Determine if string value can be converted to a float. Return True if
    value can be converted to a float and False otherwise.
    
    Parameters
    ----------
    value : string
        String value to try to convert to a float.
        
    Returns
    -------
    bool : bool
        
    Examples
    --------
    >>> import nwispy_helpers
    >>> nwispy_helpers.isfloat(value = "2.5")
    True
    >>> nwispy_helpers.isfloat(value = "hello world")
    False
    >>> nwispy_helpers.isfloat(value = "5.5_")
    False
    """
    
    try:
        float(value)
        return True
        
    except ValueError:
        return False