pandas python pandas没有连接到空的DataFrame
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python pandas not concat'ing into empty DataFrame
提问by Chrispy
I'm iterating over a DataFrame, evaluating each row and then sticking it into another DataFrameby using the concat()method. However, the receiving DataFrameis still empty.
我正在迭代 a DataFrame，评估每一行，然后DataFrame使用该concat()方法将其粘贴到另一行中。然而，接收DataFrame仍然是空的。
import pandas as pd
empty = DataFrame(columns=('col1', 'col2'))
d = {'col1' : Series([1, 2, 3]),
'col2' : Series([3, 4, 5])
}
some_data = DataFrame(d)
print empty
print some_data
print 'concat should happen below'
for index, row in some_data.iterrows():
pd.concat([empty, DataFrame(row)])
print empty # should contain 3 rows of data
OUTPUT:
输出：
Empty DataFrame
Columns: [col1, col2]
Index: []
col1 col2
0 1 3
1 2 4
2 3 5
concat should happen below
Empty DataFrame
Columns: [col1, col2]
Index: []
回答by Alvaro Fuentes
You need to update emptyif you want it to stores the values: empty = pd.concat([empty, DataFrame(row)])Also you can concatenate the whole DataFrames, try this print pd.concat([ empty,some_data])
empty如果您希望它存储值，则需要更新：empty = pd.concat([empty, DataFrame(row)])您也可以连接整个DataFrames，试试这个print pd.concat([ empty,some_data])
If you want to filter the rows you can try this:
如果你想过滤行，你可以试试这个：
def f(r):
#check the row here
return True #returns True or False if include/exclude the row
print some_data.groupby(some_data.index).filter(f)
