使用python返回excel中两个不同文件中两列之间的差异

Question

我有两个 csv 文件，其中有一个名为“名称”的公共列。文件 2 将不断更新并在列中随机添加新值。我如何编写脚本来比较两列并找到差异，而不管新值放在 file2 中的什么位置。

其他解决方案只有在新值位于列末尾而不是在列内随机时才会发现差异。

我尝试过的代码（只在列底部输出新值，而不是在列中随机输出时）：

df1 = pd.read_csv('file1.csv')
df2 = pd.read_csv('file2.csv')

new_df = (df1[['Name']].merge(df2[['Name']],on='Name',how = 'outer',indicator = True)
                       .query("_merge != 'both'")
                       .drop('_merge',axis = 1))

new_df.to_csv('file4.csv')

文件1：

Name     
gfd454
3v4fd
th678iy

文件2：

Name     
gfd454
fght45
3v4fd
th678iy

输出应该是：

Name
fght45

Answer 1

# df1 original dataframe of File_1 data
df1 = pd.DataFrame({'Name':[ 'gfd454' , '3v4fd', 'th678iy']})

# df2 dataframe of changing File_2 data
df2 = pd.DataFrame({'Name':[ 'gfd454' , 'abcde', 'fght45', '3v4fd', 'abcde' ,'th678iy', 'abcde']})

# Assuming df1 comprises distinct elements and doesn't change, and that
# df2 contains all elements of df1 and more (the new updates) 
# df2 may have duplicates like 'abcde'

# Drop duplicates in df2, if df1 has duplicates also drop it first
# ``keep = first`` : Drop duplicates except for the first occurrence.
df2.drop_duplicates(keep='first', inplace=True)
print(df2)

# pandas.concat adds elements of df2 to df1, even if it already exists in df1
df_concat = pd.concat([df1,df2], join='outer', ignore_index = True)
print(df_concat)

# now drop the duplicates between df1, df2
df_diff = df_concat .drop_duplicates(keep=False)
print(df_diff)

现在，问题在于您必须确保 df1-df2 = {}， 即 df1 是 df2 的子集

Answer 2

使用左侧的文件 2 进行左连接。之后，提取不匹配的 NaN 行。

Answer 3

如果您只想检查一列，可以通过比较两个列表来尝试：

list1=df1['Name'].tolist()
list2=df2['Name'].tolist()
s = set(list1)
diff = [x for x in list2 if x not in s]