binance basic rounding example

binance_rounding.py

from math import floor

def get_purchase_quantity( raw_quantity:float, step_size:str ) -> float:
	if float( step_size ) % 1 == 0:
		return round( raw_quantity / float( step_size ) ) * float( step_size )

	return round( raw_quantity, step_size.index( '1' ) - 1 )

def get_sale_quantity( raw_quantity:float, step_size:str ) -> float:
	if float( step_size ) % 1 == 0:
		return floor( raw_quantity / float( step_size ) ) * float( step_size )

	multiplier = 10 ** ( step_size.index( '1' ) - 1 )

	return floor( raw_quantity * multiplier ) / multiplier

def main():

	step_sizes = [
		'1.00',
		'1.00000000',
		'0.10000000',
		'0.01000000',
		'0.00100000',
		'0.00010000',
		'0.00001000',
		'0.00000100',
		'10.00000000'

	]


	raw_quantity = 38.9365461

	print( f'When raw quantity equals: { raw_quantity }' )

	for step_size in step_sizes:
		purchase_quantity = get_purchase_quantity( raw_quantity, step_size )
		sale_quantity = get_sale_quantity( raw_quantity, step_size )
		print( f'\n\tstep size:{step_size}, {purchase_quantity=},{sale_quantity=}\n')

if __name__ == '__main__':
	main()