Referring to previous results

[Ingo Dahn]

From the net I got that the result of the previous computation can be referred to as _. But if I try to use it in SageCell like in

1+2

_+5

I get an error. What is the correct way to refer to previous results?

[Andrey Novoseltsev]

I never used or saw _ used in SageMathCell. There is a question of what "previous computation" is. Since I am used to SageNB, for me previous computation is the result of the previous cell, which does not make much sense when there is only one cell ;-)

I don't think that SageMathCell has any special treatment for _ on its own, so if it does or does not work, it is due to Sage/IPython/Jupyter/etc handing actual code and output. So - if things worked before and got broken I'll try to fix them, but if they never worked I claim that it is by design and should not be impemented.

[Rob Beezer]

Maybe it is a *convention* that "_" is the previous result.

"_" is a legitimate variable name in Python, so it is sometimes used for results
you don't really intend to keep.

The following produces 8 in the Sage Cell:

_ = 1 + 2
_ + 5

Rob

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[Andrey Novoseltsev]

On Tuesday, 11 April 2017 16:53:48 UTC-6, Robert Beezer wrote:

Maybe it is a *convention* that "_" is the previous result.

"_" is a legitimate variable name in Python, so it is sometimes used for results
you don't really intend to keep.

The following produces 8 in the Sage Cell:

_ = 1 + 2
_ + 5

Rob

Well, it is a convention that _ is automatically assigned the last result and on Sage command line you can do

sage: 1 + 2
3
sage: _ + 5
8

My point was that there are two separate computations here, but when entered in a single cell these two lines make "one computation", so _ does not get any value (also 3 is not displayed since only the last result is shown).