Python: how to use attribute from differenct class

I have some basic class Trader in trader.py:

Trader

trader.py

class Trader(object):
def __init__(self, exchange_name, api_key, api_secret):
self.Exchange = Exchange(exchange_name, api_key, api_secret).exchange


and a class Exchange in exchange.py

Exchange

exchange.py

class Exchange(object):
def __init__(self, name, api_key, api_secret):
self.name = name
exchange_id = name
exchange_class = getattr(ccxt, exchange_id)
self.exchange = exchange_class(
'apiKey': api_key,
'secret': api_secret,
'timeout': 30000,
'enableRateLimit': True,
)


The above works. So I can use self.Exchange inside the Trader class to use functions against the exchange. But it works only because of this line:

self.Exchange

self.Exchange = Exchange(exchange_name, api_key, api_secret).exchange


I don't like the fact I have to put .exchange after it. I'm just a bit playing and learning python. I'm not very experienced in python programming / I'm also not a coin trader, but I liked the ccxt package.

How can I make this work without needing to putting the .exchange behind my Exchange(...) or is this normal behaviour? Or do I have to make my exchange class in a different way?

.exchange

Thanks

__new__()

__init__()

2 Answers
2

Since exchange is an attribute of an instance of the Exchange class, this is normal behavior.

exchange

Exchange

If you want to access exchange without needing to put .exchange after your Exchange object, you might consider doing away with the Exchange class entirely—since it seems you only use it to get the instance of the exchange_class from ccxt—and writing a function instead.

exchange

.exchange

Exchange

Exchange

exchange_class

Here's an example:

def get_exchange(exchange_name, api_key, api_secret):
exchange_class = getattr(ccxt, exchange_id)
return exchange_class(
'apiKey': api_key,
'secret': api_secret,
'timeout': 30000,
'enableRateLimit': True,
)

class Trader:
def __init__(self, exchange_name, api_key, api_secret):
self.exchange = get_exchange(exchange_name, api_key, api_secret)


This way an exchange will be accessible directly by instances of Trader.

exchange

Trader

exchange

Exchange

Trader.__init__

self.exchange = Exchange(...)

Exchange

exchange_class

you need to create an instance if you would like to use an attribute from another class

myInstance = Exchange()
print(myInstance.exchange_id) if you would like to print the name


the scope is local you could also declare a variable global before assigning its value if you would like to use it outside the function or class it is created in

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