使用Pandas计算大型数据帧中第n和第n-1个值之间的差异的Pythonic方法？

import pandas as pd

df = pd.DataFrame({'A': [1, 2, 3, 4, 5]})

df['B'] = df['A'].shift(1)

df['差异'] = df['A'] - df['B']

import pandas as pd

df = pd.DataFrame({'A': [1, 2, 3, 4, 5]})
df['B'] = df['A'].shift(1)
df['差异'] = df['A'] - df['B']

print(df)

   A    B   差异
0  1  NaN  NaN
1  2  1.0  1.0
2  3  2.0  1.0
3  4  3.0  1.0
4  5  4.0  1.0