在不改變原始數據框的情況下創建數據框副本

Question

我試圖創建一個函數，可以在不更改原始數據框的情況下更改數據框副本的值。這是我到目前爲止有：

def home_undervalued(df): 
    local_df = df 
    local_df['total_games'] = 0 
    local_df['total_wins'] = 0 
    cond_1 = local_df['predicted_spread'] > local_df['vegas_spread'] 
    cond_2 = local_df['actual_spread'] > local_df['vegas_spread'] 
    cond_3 = local_df['predicted_spread'] - local_df['vegas_spread'] >= 3 

    local_df.loc[cond_1 & cond_3 , 'total_games'] = 1 
    local_df.loc[cond_1 & cond_2 & cond_3 , 'total_wins'] = 1 

    total_games = sum(local_df.total_games) 
    total_wins = sum(local_df.total_wins) 

    return float(total_wins)/float(total_games) 

我然後調用函數

home_undervalued(df) 

看來工作，但後來我意識到了DF值[「total_games」]和df [」 total_wins']已經改變。我試圖改變local_df的值，但保留值df。有想法該怎麼解決這個嗎？

Answer 1

local_df = df只是創建了一個參考df名爲local_df。如果你想創建一個完整的其他數據框（順便說一下，我不建議），你可以創建一個新的數據框，如df.copy(deep=True)

Answer 2

只需使用的DataFrame

local_df = df.copy(deep=True) 

copy方法在這一行以後在local_df將存儲的df副本。