Shenlei151 flexibility enhance

[shenlei515]

Fixes #481
I adjust a few lines of code in FinRL to make it more flexible for problems that I met with in my own project, though these changes may be aiming for my project, I think it might be useful to extend the feature of FinRL including:
feature extension:

1. support different costs_pct with different stocks(fix it by modifying finrl/finrl_meta/env_stock_trading/env_stocktrading.py function init)
2. able to hold stocks when initial instead of only cash(fix it by modifying finrl/finrl_meta/env_stock_trading/env_stocktrading.py function init)
3. support to define time that trading is forbidden(fix it by modifying finrl/finrl_meta/env_stock_trading/env_stocktrading.py function _buy_stock and function _sell_stock)
4. able to get state of everyday when trading(fix it by adding finrl/finrl_meta/env_stock_trading/env_stocktrading.py function save_state_memory and finrl/drl_agents/stablebaselines3/models.py function DRL_prediction)
   bug:
   5.fix bug that when buying stocks it didn't consider conmmision, which will cause the cash < 0 (fix it by modifying finrl/finrl_meta/env_stock_trading/env_stocktrading.py function _buy_stock)
   These features are needed in my project, I hope it will help enhance the flexibility of FinRL
   Also, I put part of my project code to explan why and how to use the features that I add in RL_stock.py, I hope it will help you understand the changes I made.

[zhumingpassional]

Thanks for your codes.

It's great. I suggest to add type hint in all functions. In the new version, type hint will be added.

[YangletLiu]

@shenlei515 some research team contacted me about errors, they have a submission ddl, so I reverted this PR.

[shenlei515]

@shenlei515 some research team contacted me about errors, they have a submission ddl, so I reverted this PR.

Yes, I see some errors caused by my changes, I think my change only apply to my situation, maybe it need some modifications to be adapted for other situations. I am sorry for the result caused by my unreasonable PR.

[YangletLiu]

It is OK, not a big issue.
We may need to make the codes more standard so that everybody can contribute more easily.

[zhumingpassional]

@shenlei515
Could you please describe the function of RL_stock.py? How to use it? Could you provide an example (code)?
Thanks you very much.

In addition, I think RL_stock.py is not suitable to be in the current folder.

[zhumingpassional]

Thanks for your codes.

I have several questions. What's the length of initial_list? What does initial_list mean?

[shenlei515]

@zhumingpassional
RL_stock is a example to explain how to use the changed RLlib and why I need to modify the RLlib

First element of initial_list is the cash we have in the beginning, rests of it are the share of stocks we have at first. So the length of initial_list is supposed to be 1+stock_dimension.

[zhumingpassional]

@shenlei515

Thanks for your reply.

I suggest initial_list is seperated to two parts (parameters), initial_amount and num_stock_shares, since they have different units/denotations (money, and num of shares).

[shenlei515]

@shenlei515

Thanks for your reply.

I suggest initial_list is seperated to two parts (parameters), initial_amount and num_stock_shares, since they have different units (money, and num of shares).

Yes, that make more sense.

[zhumingpassional]

@shenlei515 Could you please push a PR to revise it if you have enough time? The first PR focuses on this point (initial_list is seperated to two parts). A PR with small changes is more favorable.

[shenlei515]

I have pulled a request to revise it.

[zhumingpassional]

Merged. Thanks for your valuable codes.