如何将 select 的第一个元素存储在元组列表中？

Question

I need to extract/clear values stored in a list of tuples, keeping only the first (left) record for each element in parentheses.

I'll put the current tables and how I need the information so it's easier to see the problem.

Current df:

ID	chords
1	[(N, 0.371519274), (A7, 0.464399092)]
2	[(N, 0.371519274), (Em, 0.464399092)]

Desired df:

ID	chords
1	N, A7
2	N, Em

Is this desired df possible?

Answer 1

Assuming the values of chords column are lists of tuples

df['chords'] = df['chords'].map(lambda lst: ", ".join(tup[0] for tup in lst))

Answer 2

df['chords'] = df['chords'].astype('str').str.split(r'[\[\](), ]+').apply(lambda x: (x[1], x[3]))

Output:

>>> df
   ID   chords
0   1  (N, A7)
1   2  (N, Em)

Answer 3

df['chords'] = df['chords'].str.extract('\(([^,]+).+\(([^,]+)').apply(tuple, axis=1)
print(df)

   ID   chords
0   1  (N, A7)
1   2  (N, Em)