How to create a method/function/attribute that checks if quotebar/tradebar is bearish or bullish

Hi Bertram,

First thing you can do is use this code to determine bearish/bullish:

if bar.Close > bar.Open: #bullish

if bar.Open > bar.Close: #bearish

But beware because bar.Open can also be == to bar.Close… and then, your algo will see neither bearish or bullish which can affect what you do thenafter.

Now, in Python you can dynamically add attributes to objects. So you can do:

...
bar = ...
if bar.Close > bar.Open:
	bar.isBull = True
	bar.isBear = False
if bar.Close < bar.Open:
	bar.isBull = False
	bar.isBear = True

Thereafter, you can use:

if bar.isBear:
	...
if bar.isBull:
	...

Beware that your attributes have not been added to the class defining “bar” (TradeBar most likely). So doing the above won't add isBear and isBull to all “bars”. Just the single one there. But if your algo adds the attributes consistently, it will work. It's not elegant, but it works.

You can also dynamically add attributes to classes in Python. But as I never tested that in LEAN which involves Python.NET to bridge between Python and C#, I don't know if it works - plus, it is an advanced subject anyway.

Finally, because TradeBar (say it is what you are using here) is public, you can inherit from it and define your two additional attributes in it. Then, you would want to look at inheritance in Python. It's less advanced than dynamically adding attributes to classes but it is not something that can be summarized in a post like this one.

Hope this helps,

Fred

Thank you so much. This was very insightful.

However, I just spent some time looking in to inheritance, and it looks like the way to go. But there is one thing that stops me.

Say i want to create a class called SignalBar as a subclass of TradeBar, or inheriting the TradeBar class. I would do it like this:

class SignalBar(TradeBar):
	def __init__(????):
		super().__init__(????)
		if SignalBar.Close < SignalBar.Open:
			SignalBar.isBear = True
		elif SignalBar.Close > Signal.Open:
			SignalBar.isBull =True
		else:
			SignalBar.isBull = False
			SignalBar.isBear = False

Or something like that. What my problem is that everywhere I search, people seem to define the __init__ method with specific arguments.

But since I don't know where to find the original TradeBar class, I do not know what to write in the __init__ .

Would it be possible to write it like so:

class SignalBar (TradeBar):
	def __init__(TradeBar):
		...

I know this is a bunch of newbie questions. However, being able to ask questions directly to quantconnect-users, really gives much more insight and understanding than taking a course online or reading all of stackoverflow haha. At least thats what I've found.

Thanks for your time and help,

Bertram

Hi Bertram,

Glad it helped.

I answered your last post in your other thread… https://www.quantconnect.com/forum/discussion/13207/inheriting-classes

Fred