如何创建For循环来检查一个列是否在Pandas DataFrame中包含重复项?

Question

我试图创建一个for循环，首先检查检查一列('col1')是否有重复项，如果为真，将另一列('col2')的值添加到('col1')。

下面的语句工作，然而，所有('col1')值被视为重复。我确定这一列中很少有重复的，但不知何故，这个语句一直返回真。我认为问题出在第二行包含.duplicated()

的那一行

import pandas as pd
tuple = [['Jake','NY'],['Tom','Montana'],['Hannah','Cali'],['Jason','Boston'],['Tom','Washington'],['Hannah','Florida']]
df = pd.DataFrame(tuple, columns=('col1', 'col2'))
for i in df['col1']:
if df['col1'].duplicated().any():
df['col1'] = df['col1'] + ' - ' +  df['col2']

Answer 1

您可以使用duplicate找到重复的值，如您在示例中所示，这可以使用loc:

作为过滤器使用df.loc[df['col1'].duplicated(keep=False), 'col1']

你可以用一个新值来替换这些值:

temp = df['col1'] + ' - ' + df['col2']
df.loc[df['col1'].duplicated(keep=False), 'col1'] = temp

以OP:

为例

import pandas as pd
tuple = [['Jake','NY'],['Tom','Montana'],['Hannah','Cali'], ['Jason','Boston'],['Tom','Washington'],['Hannah','Florida']]
df = pd.DataFrame(tuple, columns=('col1', 'col2'))
temp = df['col1'] + ' - ' + df['col2']
df.loc[df['col1'].duplicated(keep=False), 'col1'] = temp
df

col1                col2
Jake                NY
Tom - Montana       Montana
Hannah - Cali       Cali
Jason               Boston
Tom - Washington    Washington
Hannah - Florida    Florida