Split / Explode a column of dictionaries into separate columns with pandas
dictionary, json, json-normalize, pandas, python
Solution
To convert the string to an actual dict, you can do `df['Pollutant Levels'].map(eval)`. Afterwards, the solution below can be used to convert the dict to different columns.
Using a small example, you can use `.apply(pd.Series)`:
In [2]: df = pd.DataFrame({'a':[1,2,3], 'b':[{'c':1}, {'d':3}, {'c':5, 'd':6}]})
In [3]: df
Out[3]:
a b
0 1 {u'c': 1}
1 2 {u'd': 3}
2 3 {u'c': 5, u'd': 6}
In [4]: df['b'].apply(pd.Series)
Out[4]:
c d
0 1.0 NaN
1 NaN 3.0
2 5.0 6.0
To combine it with the rest of the dataframe, you can `concat` the other columns with the above result:
In [7]: pd.concat([df.drop(['b'], axis=1), df['b'].apply(pd.Series)], axis=1)
Out[7]:
a c d
0 1 1.0 NaN
1 2 NaN 3.0
2 3 5.0 6.0
Using your code, this also works if I leave out the `iloc` part:
In [15]: pd.concat([df.drop('b', axis=1), pd.DataFrame(df['b'].tolist())], axis=1)
Out[15]:
a c d
0 1 1.0 NaN
1 2 NaN 3.0
2 3 5.0 6.0
Problem
I have data saved in a `postgreSQL` database. I am querying this data using Python2.7 and turning it into a Pandas DataFrame. However, the last column of this dataframe has a dictionary of values inside it. The DataFrame `df` looks like this: ``` Station ID Pollutants 8809 {"a": "46", "b": "3", "c": "12"} 8810 {"a": "36", "b": "5", "c": "8"} 8811 {"b": "2", "c": "7"} 8812 {"c": "11"} 8813 {"a": "82", "c": "15"} ``` I need to split this column into separate columns, so that the DataFrame `df2 looks like this: ``` Station ID a b c 8809 46 3 12 8810 36 5 8 8811 NaN 2 7 8812 NaN NaN 11 8813 82 NaN 15 ``` The major issue I'm having is that the lists are not the same lengths. But all of the lists only contain up to the same 3 values: 'a', 'b', and 'c'. And they always appear in the same order ('a' first, 'b' second, 'c' third). The following code USED to work and return exactly what I wanted (df2). ``` objs = [df, pandas.DataFrame(df['Pollutant Levels'].tolist()).iloc[:, :3]] df2 = pandas.concat(objs, axis=1).drop('Pollutant Levels', axis=1) print(df2) ``` I was running this code just last week and it was working fine. But now my code is broken and I get this error from line [4]: ``` IndexError: out-of-bounds on slice (end) ``` I made no changes to the code but am now getting the error. I feel this is due to my method not being robust or proper. Any suggestions or guidance on how to split this column of lists into separate columns would be super appreciated! EDIT: I think the `.tolist()` and .apply methods are not working on my code because it is one Unicode string, i.e.: ``` #My data format u{'a': '1', 'b': '2', 'c': '3'} #and not {u'a': '1', u'b': '2', u'c': '3'} ``` The data is imported from the `postgreSQL` database in this format. Any help or ideas with this issue? is there a way to convert the Unicode?