python trading bot( paper trading)

Question

So I am writing a trading bot in python. It is more for fun and I just started. Every method works alone, so I excluded them here, to not give you 300lines of Code. I also exclude the hole analyze method, since even if I clear the rest of the method, the same Error appears. When I use analyze just once, it doesn't do anything but also gets no error and when I use it in a loop I get an error:  Exception has occurred: KeyError 'result' (mark get_crypto_data)

This doesn't make sense to me, since if I print get_crypto_data it works just fine.

def get_crypto_data(pair,since):
    return api.query_public("OHLC", data = {"pair" : pair, "since" : since})["result"][pair] #array of prices (60sek)

def analyze(pair,since):
    data = get_crypto_data(pair[0]+pair[1], since)

if __name__ == "__main__":
    api = krakenex.API()
    api.load_key("KrakenKey.txt")
    pair = ('XETH' , 'ZEUR')   # Currency pair 
    since = str(int(time.time() - 3600))  
     
    while True:
         analyze(pair,since)

The data structure receiving from the API looks like this(example)(without indents):

{
"error": [ ],
"result": {
"XXBTZUSD": [
[
1616662740,
"52591.9",
"52599.9",
"52591.8",
"52599.9",
"52599.1",
"0.11091626",
5
],
[
1616662800,
"52600.0",
"52674.9",
"52599.9",
"52665.2",
"52643.3",
"2.49035996",
30
],
[
1616662860,
"52677.7",
"52686.4",
"52602.1",
"52609.5",
"52634.5",
"1.25810675",
20
],
[
1616662920,
"52603.9",
"52627.5",
"52601.2",
"52616.4",
"52614.0",
"3.42391799",
23
],
[
1616662980,
"52601.2",
"52601.2",
"52599.9",
"52599.9",
"52599.9",
"0.43748934",
7
]
],
"last": 1616662920
}
}

Answer 1

Context

A KeyError in Python is raised when you try to search for an item in an object that doesn't exist. For example, if you make a request:

response = requests.get(url).json()
response['nonexistent']
# KeyError raised as nonexistent doesn't exist in the object

With that in mind, a KeyError when you make an API call to receive this object:

api.query_public("OHLC", data = {"pair" : pair, "since" : since})

We can infer that for whatever reason, ["result"] is not a key in the object above. To debug the issue, follow the steps below.

Debugging

1. Make the API call and save the response to a variable. Then print the variable along with its type to understand how you can interact with it.

response = api.query_public("OHLC", data = {"pair" : pair, "since" : since})
print(response, type(response))

2. If it's in a String format (or another standard convertible format), you can use the inbuilt json library to convert it to a dictionary object you can call as you did in your example.

import json

response = api.query_public("OHLC", data = {"pair" : pair, "since" : since})
response = json.loads(response)

3. Otherwise, given the structure of the output you displayed, it may be wise to convert the response to a string and then follow step 2.

import json

# Get the response
response = api.query_public("OHLC", data = {"pair" : pair, "since" : since})

# Convert to string
response = str(response)

# Convert to dictionary using JSON
response = json.loads(response)

# Call the data you want
data = response["result"]["XXBTZUSD"]