def validate_float(data):
	"""
	Checks if data contains something that can be used as float:
	- string containing float
	- int
	- float itself
	and converts it to float.

	Return:
	- float if possible
	- 0.0 if empty string
	- None if float not possible
	"""

	if isinstance(data, str):
		if len(data) > 0:
			if data.lstrip('-').replace('.', '').isdigit():
				return float(data)
		else:
			return 0.0
	elif isinstance(data, float):
		return data
	elif isinstance(data, int):
		return float(data)
	else:
		return None