madx set_value has a odd output about cpymad

[coldfix]

Post full minimal example.

Specify set value argument as number, not as string.

[coldfix]

Ah you just took the example from set_value docstring and executed it without even defining a quadrupole element named R1QS1, right? ...

Sorry for being rude, but you are really asking for a lot of stuff, that should be obvious if you had some knowledge about python + madx. If you don't have that, I don't see any reason for you to use this library, and you really should start using plain MAD-X first without cpymad / madgui.

[Landau1908]

Hi,
still don't work.

In [46]: madx.set_value('R1QS1->K1', 42)

In [47]: madx.evaluate('R1QS1->K1')
Out[47]: 
0.0



[coldfix]

Still didn't post a full example.

[Landau1908]

I have learned madx and python for 3 months, but I don't know a lot of cpymad. So, if I trouble you very much, very sorry for that.
I really want to understand cpymad.

[Landau1908]

sorry, it is just a simple example from set_value docstring.

[coldfix]

Okay, then please focus more on providing full information, i.e. all the code/files that is needed to reproduce your problem. In this particular case, the example should start with from cpymad.madx import Madx and end with madx.evaluate(...). I don't want to ask you back for all the necessary information everytime.

Initially, I thought, you were working on some sequence, which you didn't post. Now I have to assume, you are executing this without a sequence. But this is still just guessing.

This specific example shows how to set the K1 attribute of a quadrupole named R1QS1. If you want to set a constant value, just use an identifier name, e.g.:

madx.set_value('EULER', 2.718)
madx.evaluate('EULER')

[Landau1908]

If replace R1QS1->K1 with R1QS1, it works. Why?

In [48]: madx.set_value('R1QS1', 42)

In [49]: madx.evaluate('R1QS1')
Out[49]: 

42.0

[coldfix]

From now on, please follow the guidelines here https://github.com/hibtc/cpymad#reporting-issues and you will be fine. Otherwise I will limit my responses to you to only one in a few days, so make sure that your questions can be fully understood without asking back.