I have this code to plot PSD of a signal – but are encountering the below error looping over the peaks returned by signal.find_peaks to then annotate the frequency on the plot.

Note: that the signal.find_peaks returns the indices which I am then converting to a frequency (peak_freqs) before plotting on x axis with:

((peak/1024)*sample_rate) + (center_freq-(sample_rate/2))

The juypter notebook for the plot is:

from scipy import signal
import numpy as np
from matplotlib import pyplot as plt

samples = np.fromfile('test.fc32', dtype=np.complex64)
sample_rate = 768000
center_freq = 160500000
size = len(samples)
x = samples

fft_freqs = np.linspace(sample_rate / -2, sample_rate / 2, 1024) + center_freq
psd = plt.psd(x, NFFT=1024, Fs=768000, Fc=160500000)
peaks = signal.find_peaks(psd[0], prominence=0.000000000001),
for peak in peaks[0]:
    peak_freq =  ((peak/1024)*sample_rate) + (center_freq-(sample_rate/2))
    plt.annotate("test", xy=(peak_freq , -115))
plt.show()

Which creates this plot:

However I get an error:

[1.6033875e+08 1.6050525e+08 1.6060125e+08 1.6070775e+08]
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[37], line 17
     15 peaks = signal.find_peaks(psd[0], prominence=0.000000000001),
     16 for peak in peaks[0]:
---> 17     peak_freq =  ((peak/1024)*sample_rate) + (center_freq-(sample_rate/2))
     18     print ( peak_freq)
     19     plt.annotate("test", xy=( peak_freq , -115))

TypeError: unsupported operand type(s) for /: 'dict' and 'int'
Error in callback <function _draw_all_if_interactive at 0x00000222FDD080E0> (for post_execute), with arguments args (),kwargs {}:
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
File ~AppDataLocalPackagesPythonSoftwareFoundation.Python.3.11_qbz5n2kfra8p0LocalCachelocal-packagesPython311site-packagesmatplotlibpyplot.py:197, in _draw_all_if_interactive()
    195 def _draw_all_if_interactive() -> None:
    196     if matplotlib.is_interactive():
--> 197         draw_all()

There are two errors above, one related to the type being a dict and the second fatal one probably because peak_freq ends up being an array.

How can I loop over the peaks returned from signal.find_peaks.