callback function doesn't print, unless ran by Jupyter-CodePudding

Here is the minimal code needed to reproduce the problem.

I call an API with a callback function that prints what comes out of the API call.

If I run this code in Jupyter, I get the output. If I run it with python file.py I don't get any output. I already checked the API's code, but that does nothing weird. Setting DEBUGGING to True isn't helpful either.

Note that there is once dependency; the Bitvavo API. Install it with pip install python-bitvavo-api

# %%
from python_bitvavo_api.bitvavo import Bitvavo

# %%
def generic_callback(response):
    print(f"log function=get_markets, {response=}")

bitvavo = Bitvavo({"DEBUGGING": False})
websocket = bitvavo.newWebsocket()

# %%
websocket.markets(options={"market": "BTC-EUR"}, callback=generic_callback)

Here is the expected output I get from Jupyter:

log function:get_markets, response={'market': 'BTC-EUR', 'status': 'trading', 'base': 'BTC', 'quote': 'EUR', 'pricePrecision': 5, 'minOrderInBaseAsset': '0.0001', 'minOrderInQuoteAsset': '5', 'orderTypes': ['market', 'limit', 'stopLoss', 'stopLossLimit', 'takeProfit', 'takeProfitLimit']}

CodePudding user response：

Because you're using a websocket, the callback is executed by a different thread, which means that if you don't wait, the main thread (which is to receive the print's output) will already be killed.

Add a sleep(1) (that's seconds, not ms) at the end and the output will show.

PS: The reason Jupyter does show the output, is because Jupyter keeps an interactive window open the entire time, even far after you've run the code :)

CodePudding user response：

import time
from python_bitvavo_api.bitvavo import Bitvavo

# %%
def generic_callback(response):
    print(f"log function=get_markets, {response=}")

bitvavo = Bitvavo({"DEBUGGING": False})
websocket = bitvavo.newWebsocket()

# Wait N.1 required to receive output, otherwise the main thread is killed
time.sleep(1)

# %%
websocket.markets(options={"market": "BTC-EUR"}, callback=generic_callback)

# Wait N.2 required to receive output, otherwise the main thread is killed
time.sleep(1)