Note 13 - Stock-based Compensation - Number of Shares Issued and Cash Received upon Exercise of the Stock Options (Details) - USD ($)	12 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2017
Number of Shares Issued Upon Exercise of Options (in shares)	125,879	1,094,589	264,727
Number of Options Exercised on Forfeiture Basis (in shares)	193,375	580,625	309,634
Number of Net Shares Issued (in shares)	59,629	309,589	162,227
Number of Options Exercised on Cash Basis (in shares)	66,250	785,000	102,500
Cash Received from Exercise of Stock Options	$ 72,363	$ 530,050	$ 56,925
Total Intrinsic Value of Options Exercised	$ 134,174	$ 1,049,694	$ 232,205