How can I transform a list of tuples into a pandas dataframe so that the first value of each tuple represents a column?

Question

I would like to transform my list of tuples so that the first element of each tuple represents 2 different columns. The second element of each tuple should represent the values that correspond to the columns in the pandas df.

My current list of tuples:

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list_tuples = [('G', 9.8), ('B', 4.2), ('G', 9.6), ('B', 2.3), ('G',7.6), ('B', 3.1)]

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Desired output:

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            G        B   
           9.8      4.2      
           9.6      2.3      
           7.6      3.1      

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The code I currently have which does not give desired output:

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df = pd.DataFrame(list_tuples, columns=['G', 'B'])

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Answer 1

Use defaultdict for convert list of tuples for dictionary of lists and then pass it to DataFrame constructor:

from collections import defaultdict

d = defaultdict(list)
for a, b in list_tuples:
    d[a].append(b)
df = pd.DataFrame(d)
print (df)
     G    B
0  9.8  4.2
1  9.6  2.3
2  7.6  3.1

Answer 2

Convert it to a dictionary, create your dataframe and clean it up with DataFrame.drop_duplicates and DataFrame.bfill:

list_tuples = [('G', 9.8), ('B', 4.2), ('G', 9.6), ('B', 2.3), ('G',7.6), ('B', 3.1)]

df = (pd.DataFrame([{col1:val} for col1, val in list_tuples])
        .bfill()
        .drop_duplicates('B')
        .reset_index(drop=True)
     )

     G    B
0 9.80 4.20
1 9.60 2.30
2 7.60 3.10