Note 14 - Capital Stock (Details Textual) - USD ($)				1 Months Ended	3 Months Ended		9 Months Ended
	Apr. 08, 2021	Mar. 19, 2021	Sep. 23, 2020	Jun. 08, 2021	Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2021	Apr. 30, 2020	Jan. 31, 2021	Oct. 31, 2020	Jul. 31, 2020
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)					$ 1.90		$ 1.90		$ 1.93	$ 1.92	$ 2.03
Share Price (in dollars per share)			$ 0.96
Proceeds from Warrant Exercises					$ 3,399,303		$ 3,401,193
Common Stock Issued During Period, Shares, Exercise of Warrants (in shares)					3,598,200		3,599,250
Class of Warrant or Right, Exercised During Period (in shares)					8,145,840		8,146,890
Proceeds from Stock Options Exercised					$ 1,086,844		$ 1,308,278
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period (in shares)					1,511,547		2,084,607
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value					$ 20,034,091		$ 20,034,091
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value					10,709,934		10,709,934
Share-based Compensation Arrangement by Share-based Payment Award, Options, Unvested in Period, Intrinsic Value					9,324,157		9,324,157
Share-based Payment Arrangement, Option [Member]
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total					922,396		$ 922,396
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)							1 year 21 days
Restricted Stock Units (RSUs) [Member]
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total					508,861		$ 508,861
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)							1 year 51 days
Share-based Payment Arrangement, Expense					$ 262,970	$ 66,928	$ 806,638	$ 200,784
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number, Ending Balance (in shares)					1,615,000		1,615,000				1,615,000
Performance-based Restriced Stock Units [Member]
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total					$ 126,720		$ 126,720
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)							262 days
Share-based Payment Arrangement, Expense					$ 37,544	$ 68,165	$ 112,632	$ 204,495
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number, Ending Balance (in shares)					333,750		333,750				333,750
Subsequent Event [Member]
Proceeds from Stock Options Exercised				$ 380,776
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period (in shares)				704,423
Warrant Issued with September 2020 Offering [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)			1
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)			$ 1.80
Warrants and Rights Outstanding, Term (Month)			2 years
Warrant Issued to Agents [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)	1
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)	$ 4.125		$ 1.80		$ 1.80		$ 1.80
Warrants and Rights Outstanding, Term (Month)	5 years		2 years
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)	181,818		583,333
September 2020 Offering [Member]
Number of Units Issued During Period (in shares)			12,500,000
Shares Issued, Price Per Share (in dollars per share)			$ 1.20
Proceeds from Issuance or Sale of Equity, Total			$ 15,000,000
Number of Shares per Unit Issued (in shares)			1
Number of Warrants per Unit (in shares)			0.5
At-the-market Offering [Member]
Stock Offering, Maximum Amount					$ 30,000,000		$ 30,000,000
Stock Issued During Period, Shares, New Issues (in shares)							13,668,906
Proceeds from Issuance of Common Stock, Net							$ 29,320,949
At-the-market Offering [Member] | Weighted Average [Member]
Shares Issued, Price Per Share (in dollars per share)					$ 2.19		$ 2.19
Direct Offering [Member]
Shares Issued, Price Per Share (in dollars per share)	$ 3.30	$ 3.05
Stock Issued During Period, Shares, New Issues (in shares)	3,636,364	10,000,000
Proceeds from Issuance of Common Stock, Net	$ 11,315,966	$ 29,083,710