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When I have data of quantity and buy and sell program, I want to get the cumulative quantity by adding a number when it is 'buy' and deducting a number when it is 'sell'. How can I do this in pandas? I know there is .cumsum() function to add it, but I don't know how to deduct it.

mozway
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david
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  • Can you add the data snippet as code rather than an image so that people have a [reproducible example](https://stackoverflow.com/help/minimal-reproducible-example) to work with – Sparrow0hawk Nov 03 '21 at 13:28
  • Try https://stackoverflow.com/a/49161189/874188 for a start – tripleee Nov 03 '21 at 13:29

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You can flip the integer when selling:

df['quantity'].where(df['buy&sell'].eq('buy'), -df['quantity']).cumsum()
mozway
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