pandas 如何更新数据帧值
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How to update dataframe value
提问by Mateyobi
I have a project where for each row in a table I need to iterate through rows from another table and update values in both. The changes need to stick for the next iteration. What is the best way to do that?
我有一个项目，对于表中的每一行，我需要遍历另一个表中的行并更新两个表中的值。这些更改需要在下一次迭代中保持不变。最好的方法是什么？
for invoice_line in invoices.itertuples():
qty = invoice_line.SHIP_QTY
for receipt_line in receipts[receipts.SKU == invoice_line.SKU].itertuples():
if qty > receipt_line.REC_QTY:
receipts.set_value(receipt_line.index,'REC_QTY',0)
qty = qty - receipt_line.REC_QTY
else:
receipts.set_value(receipt_line.index,'REC_QTY', receipt_line.REC_QTY - qty)
qty = 0
recd = receipt_line.REC_DATE
if qty < 1:break
invoices.set_value(invoice_line.index,'REC_DATE',recd)
set_value does not seem to work.
set_value 似乎不起作用。
import pandas as pd
import numpy as np
df = pd.DataFrame(np.random.randn(50, 4), columns=list('ABCD'))
for row in df.itertuples():
df.set_value(row.index,'test',row.D)
print df.head()
回答by John
I think what you want is a capitalized Index
我认为你想要的是大写 Index
import pandas as pd
import numpy as np
df = pd.DataFrame(np.random.randn(50, 4), columns=list('ABCD'))
for row in df.itertuples():
df.set_value(row.Index,'test',row.D)
print df.head()
回答by Sam
Not 100% sure if this is what you want, but I think you're trying to loop thru a list and update the value of a cell in a dataframe. The syntax for that is:
不是 100% 确定这是否是您想要的，但我认为您正在尝试遍历列表并更新数据框中单元格的值。其语法是：
for ix in df.index:
df.loc[ix, 'Test'] = 'My New Value'
where ix is the row position and 'Test' is the column name that you want to update. If you need to add more logic, you could try somthing like:
其中 ix 是行位置，'Test' 是您要更新的列名。如果您需要添加更多逻辑，您可以尝试以下操作：
for ix in df.index:
row = df.loc[ix]
if row.myVariable < 100:
df.loc[ix, 'SomeColumn'] = 'Less than ahundred'
else:
df.loc[ix, 'SomeColumn'] = 'ahundred or more'
