import pandas as pd

df = pd.DataFrame([[1,2,3,4],[4,5,6,7],[7,8,9,10]],
                  columns=list('abcd'), index=['가','나','다'])
print(df)

df2 = df

df2['a'] = 100
print(df)

print(id(df), id(df2))

df3 = df.copy()
df2['b'] = 333

print('-----------------------------------')
print(df)
print(df2)
print(df3)
print('-----------------------------------')

df = df + 99
print(df)
print(df2)