How to append a list to pandas column, series?

just copy the same format you used (dict) to make a dataframe like so:

import pandas as pd

d = {'col1': [1, 2], 'col2': [3, 4]}
df = pd.DataFrame(data=d)

xtra = {'col1': [3,4]}

df = df.append(pd.DataFrame(xtra))

You can also add those rows without creating annother Dataframe by iterating on xtra:

for val in xtra:
    df = df.append({'col1' : val}, ignore_index=True)

Use pd.DataFrame and DataFrame.append:

df = df.append(pd.DataFrame(xtra, columns=['col1']), ignore_index=True)

print(df)
  col1  col2
0     1   3.0
1     2   4.0
2     3   NaN
3     4   NaN