Consider the below dataframe, column c will always have an empty list in it. I need to compute few things and add it to the list, for example append values of column a and b to the empty list of column c
Given df
Expected output:
3 Answers
Let's try
df["Mark list"] = df.filter(regex='Mark\d+').agg(list, axis=1)
Comments
You'll want to use pandas.DataFrame.apply for this.
something like:
df["Mark list"] = df.apply(lambda row: [row["Mark1"], row["Mark2"]], axis=1)
1 Comment
GeekGroot
Thanks for your reply!, one more question. If I have to append mark3 to the mark list how can it be done?
You could convert the columns you want to append into lists (using a custom function and apply) and then simply add them to the list column. This will work for columns calculated on the fly as well.
import pandas as pd
df_vals = {"mark1": [23, 34, 45], "mark2": [45, 34, 12], "mark_list": [[] for i in range(3)]}
to_list = lambda x: [x]
df = pd.DataFrame(df_vals)
df["mark_list"] += df["mark1"].apply(to_list)
df["mark_list"] += df["mark2"].apply(to_list)
df["mark_list"] += (df["mark2"] + df["mark1"]).apply(to_list) # works for columns created on-the-fly
df
Output:
mark1 mark2 mark_list
0 23 45 [23, 45, 68]
1 34 34 [34, 34, 68]
2 45 12 [45, 12, 57]
