不完整筛选列

import pandas as pd

# df = pd.DataFrame()
# df["col1"] = [1] * 2
# df_filt = df[["col1"]]
# df_filt.rename(columns={"col1": "col1"}, inplace=True)  # 无warning

# df = pd.DataFrame()
# df[["col1", "col2"]] = [1] * 2
# df_filt = df[["col1", "col2"]]
# df_filt.rename(columns={"col1": "col1"}, inplace=True)  # 无warning

# df = pd.DataFrame()
# df[["col1", "col2"]] = [1] * 2
# df_filt = df[["col1"]]  # 不完整筛选列
# df_filt.reset_index(drop=True, inplace=True) # reset_index不管用
# df_filt.rename(columns={"col1": "col1"}, inplace=True)  # SettingWithCopyWarning

# df = pd.DataFrame()
# df[["col1", "col2"]] = [1] * 2
# df_filt = df[["col1"]].copy()  # 不完整筛选列
# df_filt.rename(columns={"col1": "col1"}, inplace=True)  # 必须copy