df = pd.DataFrame({'a': [1, 2, 3], 'b': [4, 5, 6]})
df.shape # 形状，格式是(行数,列数)
df.shape[0] # 行数
df.shape[1] # 列数

参考：​​https://www.geeksforgeeks.org/python-pandas-df-size-df-shape-and-df-ndim/​​