drop_duplicates - ValueError: keep 必須是“first”、“last”或 False

Question

我已經安裝了 Pandas 17.0。 我現在收到一個奇怪的錯誤

ValueError: keep must be either "first", "last" or False

當我嘗試這樣做時：

ids=ids.drop_duplicates('ID')

這在以前的 Pandas 版本中一直有效，代碼沒有改變。 BTW ids是一個包含一列整數的數據框......

這是回溯：

Traceback (most recent call last):

File "<ipython-input-34-6e98a890591b>", line 1, in <module>
     ids=ids.drop_duplicates('ID')

File "C:\Anaconda3\lib\site-packages\pandas\util\decorators.py",
 line 89, in wrapper
     return func(*args, **kwargs)

File "C:\Anaconda3\lib\site-packages\pandas\core\series.py", line
 1164, in drop_duplicates
     return super(Series, self).drop_duplicates(keep=keep, inplace=inplace)

File "C:\Anaconda3\lib\site-packages\pandas\util\decorators.py",
 line 89, in wrapper
     return func(*args, **kwargs)

File "C:\Anaconda3\lib\site-packages\pandas\core\base.py", line 576,
 in drop_duplicates
     duplicated = self.duplicated(keep=keep)

File "C:\Anaconda3\lib\site-packages\pandas\util\decorators.py",
 line 89, in wrapper
     return func(*args, **kwargs)

File "C:\Anaconda3\lib\site-packages\pandas\core\series.py", line
 1169, in duplicated
     return super(Series, self).duplicated(keep=keep)

File "C:\Anaconda3\lib\site-packages\pandas\util\decorators.py",
 line 89, in wrapper
     return func(*args, **kwargs)

File "C:\Anaconda3\lib\site-packages\pandas\core\base.py", line 603,
 in duplicated
     duplicated = lib.duplicated(keys, keep=keep)

File "pandas\lib.pyx", line 1383, in pandas.lib.duplicated
 (pandas\lib.c:24490)

ValueError: keep must be either "first", "last" or False

注意keep=keep ？ Pandas 17.0 中drop_duplicates的默認值是keep='first' 。 所以如果我不指定它不應該默認為那個嗎？ 為什么我會在這里出錯？ Pandas 17.0 中的錯誤？

Answer 1

該錯誤表明ids實際上是一個Series ，其第一個參數是keep參數，如果ids確實是一個 df 則不會發生此錯誤，因為drop_duplicates第一個參數是subset 。

Answer 2

我嘗試了語法（使用keep ），以前是take_last ...

import pandas as pd
df = pd.DataFrame({'c1': ['cat'] * 3 + ['dog'] * 4,
                   'c2': [1, 1, 2, 3, 3, 4, 4]})

print(df)
print(df.drop_duplicates())   
print(df.drop_duplicates(['c1', 'c2'],keep='first'))   
print(df.drop_duplicates(['c1', 'c2'],keep='last'))   
print(df.drop_duplicates(['c1', 'c2'],keep=False))   #drops all but one cat stays

默認情況下， drop_duplicates()它是keep='first'並且所有列都被計算drop_duplicates() 。