Doing calculations while creating a List (in Python)-CodePudding

I'm getting data from an API and storing it on Python dictionary (and then a list of dictionaries).

I need to do calculations (max, sum, divisions...) on the dictionary data to create extra data to add to the same dictionary/list.

My current code looks like this:

stream = whatever (whatever, whatever)
keywords = []

for batch in stream:
    for row in batch.results:

        max_clicks = max(data_keywords["keywords_clicks"])
        weighted_clicks = sum(data_keywords["keywords_weighted"])/sum(data_keywords["keywords_clicks"])

        data_keywords = {}
        data_keywords["keywords_text"] = row.ad_group_criterion.keyword.text
        data_keywords["keywords_clicks"] = row.metrics.clicks  
        data_keywords["keywords_conversion_rate"] = row.metrics.conversions_from_interactions_rate
        data_keywords["keywords_weighted"] = row.metrics.clicks * row.metrics.conversions_from_interactions_rate  
        data_keywords["etv"] = (data_keywords["keywords_clicks"]/max_clicks*data_keywords["keywords_conversion_rate"]) ((1-data_keywords["keywords_clicks"]/max_clicks)*weighted_clicks)
        keywords.append(data_keywords)

This doesn't work, it gives UnboundLocalError (local variable 'data_keywords' referenced before assignment). I've tried different options and got different errors.

data_keywords["etv"] is what I want to calculate ("max_clicks", "weighted_clicks" and data_keywords["keywords_weighted"] are intermediate calculations for that)

The main problem is that I need to calculate max and sum for all values inside the dictionary, then do a calculation using that max and sum for each value and then store the results in the dictionary itself.

So I don't know where to put the code to do the calculations (before the dictionary, inside the dictionary, after the dictionary or a mix)

I guess it should be possible, but I'm a Python/programming newbie and can't figure this out.

It's probably not relevant, but in case you are wondering, I'm trying to create a weighted sort (https://moz.com/blog/build-your-own-weighted-sort). And I can't use models/database to store data.

Thanks!

CodePudding user response：

You can't refer to elements of the dictionary before you create it. Move those variable assignments down to after you assign the dictionary elements.

for batch in stream:
    for row in batch.results:
        data_keywords = {}
        data_keywords["keywords_text"] = row.ad_group_criterion.keyword.text
        data_keywords["keywords_clicks"] = row.metrics.clicks  
        data_keywords["keywords_conversion_rate"] = row.metrics.conversions_from_interactions_rate
        data_keywords["keywords_weighted"] = row.metrics.clicks * row.metrics.conversions_from_interactions_rate  

        max_clicks = max(data_keywords["keywords_clicks"])
        weighted_clicks = sum(data_keywords["keywords_weighted"])/sum(data_keywords["keywords_clicks"])

        data_keywords["etv"] = (data_keywords["keywords_clicks"]/max_clicks*data_keywords["keywords_conversion_rate"]) ((1-data_keywords["keywords_clicks"]/max_clicks)*weighted_clicks)
        keywords.append(data_keywords)

CodePudding user response：

The UnboundLocalError is because you are trying to access data_keywords["keywords_clicks"] before you have declared data_keywords or set the value for "keywords_clicks".

Also, I think you need to be clearer about what data structure you are trying to create. You mention "a list of dictionaries" which I don't see. Maybe you are trying to create a dictionary of lists, but it looks like you overwrite the dictionary values each time you go through your loop.

CodePudding user response：

adding my response as an answer, as I do not have enough reputation to comment

To get rid of assignment error just move the line data_keywords = {} above max_clicks = max(data_keywords["keywords_clicks"])

Here you are trying to access a local variable before its declaration. The code in this case is trying to access a global variable which doesn't seems to exist.

stream = whatever (whatever, whatever) 
keywords = []

for batch in stream:
 for row in batch.results:    
    data_keywords = {}
    max_clicks = max(data_keywords["keywords_clicks"])
    weighted_clicks = sum(data_keywords["keywords_weighted"])/sum(data_keywords["keywords_clicks"])

    data_keywords["keywords_text"] = row.ad_group_criterion.keyword.text
    data_keywords["keywords_clicks"] = row.metrics.clicks  
    data_keywords["keywords_conversion_rate"] = row.metrics.conversions_from_interactions_rate
    data_keywords["keywords_weighted"] = row.metrics.clicks * row.metrics.conversions_from_interactions_rate  
    data_keywords["etv"] = (data_keywords["keywords_clicks"]/max_clicks*data_keywords["keywords_conversion_rate"]) ((1-data_keywords["keywords_clicks"]/max_clicks)*weighted_clicks)
    keywords.append(data_keywords)