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"""
Controlling user variables in an expression from python
**06-var-function.py**
User variables are created with the keyword `var`:
.. code-block:: scheme
(var #var (init))
The variable name must begin with a `#`.
They are computed only at initialization, but can be changed from the
python script with method calls (`varname` is a string and `value` is a
float)::
obj.setVar(varname, value)
The following example illustrates a self-modulated oscillator of which
the frequency and the feedback are controlled from the python side with
method calls.
"""
from pyo import *
s = Server().boot()
expression = """
(var #pitch 200)
(var #feed 0.5)
(define oscloop (
(let #xsin
(sin (+ (* twopi (~ $1)) (* #xsin $2))) // #xsin used before...
) // ... "let" statement finished = one-delay feedback loop!
#xsin // oscloop function outputs #xsin variable
)
)
(oscloop #pitch #feed)
"""
expr = Expr(Sig(0), expression, mul=0.5)
expr.editor()
# Shows two sliders, one for the frequency and one for the feedback parameter.
pit = Sig(200)
pit.ctrl([SLMap(100, 1000, "log", "value", 200)], title="Frequency")
feed = Sig(0.5)
feed.ctrl([SLMap(0, 1, "lin", "value", 0.5)], title="Feedback")
def change():
"Sends new values to user variables in the expression."
expr.setVar(["#pitch", "#feed"], [pit.get(), feed.get()])
# Calls the change() function every 20 ms to update the user variables.
pat = Pattern(change, 0.025).play()
sc = Scope(expr)
pan = Pan(expr).out()
s.gui(locals())
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