IDL WHERE in python?

Question

I am having trouble translating an old IDL script to python- my issue lies in understanding exactly how to interpret IDL's "WHERE" function.

Here is my code:

FUNCTION noise,day,y

N = N_ELEMENTS(y)
valid = WHERE(ABS(day[0:N-3]-day[2:N-1]) LT 20,cc)
IF cc LT 2 THEN RETURN,[-9.99,-9.99,-9.99,-9.99]

y_int = (y[0:N-3] * (day[2:N-1] - day[1:N-2]) + y[2:N-1] * (day[1:N-2] - day[0:N-3]))/ (day[2:N-1] - day[0:N-3])
dif  = ABS(y_int - y[1:N-2])
difR = ABS(y_int/y[1:N-2] - 1.)

dif = dif [valid]
difR= difR[valid]

; Remove 5% of higher values
Nv = LONG(cc*0.95)
s = SORT(dif) & s = s[0:Nv-1]
noise5 = SQRT(TOTAL(dif[s]^2)/(Nv-1)) ; Absolu Noise minus 5% of higher values
noise = SQRT(TOTAL(dif^2)/(cc-1)) ; Absolu Noise

s = SORT(difR) & s = s[0:Nv-1]
noiseR5 = SQRT(TOTAL(difR[s]^2)/(Nv-1)) ; Relative Noise minus 5% of higher values
noiseR = SQRT(TOTAL(difR^2)/(cc-1)) ; Relative Noise

RETURN,[noise5,noiseR5*100.,noise,noiseR*100.]

END 

Can anyone help me understand the python equivalent? TY.

Answer 1

I would translate:

valid = WHERE(ABS(day[0:N-3]-day[2:N-1]) LT 20,cc)

as:

valid = (numpy.abs(day[0:-2] - day[2:]) < 20).nonzero()