Python-科学计算-pandas-06-Df合并

import pandas as pd
dict_1 = {"time": ["2019-11-2", "2019-11-2", "2019-11-2"],          "pos": ["P1", "P2", "P3"],          "value1": [0.5, 0.8, 1.0]}
df_1 = pd.DataFrame(dict_1, columns=["time", "pos", "value1"])

dict_2 = {"pos": ["P1", "P2", "P3", "P4"],          "value2": [-1, -2, -3, -4],          "value3": [1, 2, 3, 4]}
df_2 = pd.DataFrame(dict_2, columns=["pos", "value2", "value3"])
print("\ndf_1")print(df_1)
print("\ndf_2")print(df_2)
df_merge_1 = pd.merge(df_1, df_2, how='left', on='pos')print("\ndf_merge_1")print(df_merge_1)
df_merge_2 = pd.merge(df_2, df_1, how='left', on='pos')print("\ndf_merge_2")print(df_merge_2)