Note 13 - Stock-based Compensation - Schedule of Outstanding Non-vested Stock Options (Details) - $ / shares	12 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2017
Balance, Number of Unvested Stock Options (in shares)	3,479,500	765,750	2,323,000
Nonvested, Weighted Average Grant-Date Fair Value (in dollars per share)	$ 0.68	$ 0.58	$ 0.51
Granted, number of stock options (in shares)	2,006,350	4,083,000	672,500
Granted, Weighted Average Grant-Date Fair Value (in dollars per share)	$ 0.53	$ 0.68	$ 0.77
Vested, Number of Unvested Stock Options (in shares)	(2,055,250)	(1,303,000)	(2,224,750)
Vested, Weighted Average Grant-Date Fair Value (in dollars per share)	$ 0.68	$ 0.65	$ 0.56
Forfeited, Number of Unvested Stock Options (in shares)	(120,000)	(66,250)	(5,000)
Forfeited, Weighted Average Grant-Date Fair Value (in dollars per share)	$ 0.67	$ 0.62	$ 0.49
Balance, Number of Unvested Stock Options (in shares)	3,310,600	3,479,500	765,750
Nonvested balance, Weighted Average Grant-Date Fair Value (in dollars per share)	$ 0.59	$ 0.68	$ 0.58