[Python] to append/insert data into a list/array

import pandas as pd

data = [[-4, -3, -2, -1], [1, 2, 3, 4]]
data2 = [5, 6, 7, 8]
data3 = [9, 10, 11, 12]

data_list = []
data_list.append(data)
print(data_list)

data_list.append(data2)
print(data_list)

data_list.insert(0, data3)
print(data_list)
print()

# add header (title row) using pandas
df = pd.DataFrame(data, columns=['A', 'B', 'C', 'D'])
print(df, "\n")

temp_df = pd.DataFrame([data2], columns=['A', 'B', 'C', 'D'])
df = pd.concat([df, temp_df]).reset_index(drop=True)
print(df, "\n")

temp_df = pd.DataFrame({"A": data3[0], "B": data3[1], 'C': data3[2], 'D': data3[3]}, index=[0])
df = pd.concat([temp_df, df]).reset_index(drop=True)
print(df, "\n")

# add a new column using pandas
size = len(df)
data2 = [i * 2 for i in range(size)]
temp = pd.Series(data2, name='XYZ')
df = df.join(temp)
print(df)