Creating python list in R via reticulate

Question

I would like to split a wave file using python via reticulate in R, a sample script is extracted from Python, How to split a .wav file into multiple .wav files

 from pydub import AudioSegment
    t1 = t1 * 1000 #Works in milliseconds
    t2 = t2 * 1000
    newAudio = AudioSegment.from_wav("oldSong.wav")
    newAudio = newAudio[t1:t2]
    newAudio.export('newSong.wav', format="wav")

I did similarly using R as below:

library(dplyr)
library(tidyr)
library(reticulate)
use_python('/usr/bin/python3',required = TRUE)
py_config()
pydub.py <- import('pydub')
time.start <- as.numeric(data.df.st02[loop,'time_start'])*1000
time.end <- as.numeric(data.df.st02[loop,'time_end'])*1000
new.audio <- pydub.py$AudioSegment$from_wav('142533.wav')

But returned the following error:

> new.audio[1:2]
 Error in py_call_impl(callable, dots$args, dots$keywords) : 
  TypeError: can only concatenate list (not "int") to list

Can anyone enlighten me on how to write [t1:t2] in R?

"I did similarly using R": please share all the code you used. — nicola
– nicola, Commented Mar 29, 2019 at 15:25

nicola · Accepted Answer · 2019-03-31 19:04:00Z

4

The python subset operator is a wrapper of the __getitem__ method and the : is a wrapper to create a slice object. You have to import the builtins module. Try this:

require(reticulate)
use_python('/usr/bin/python3',required = TRUE)
pydub.py <- import('pydub', convert=FALSE)
pybuiltins <- import_builtins(convert=FALSE)
new.audio <- pydub.py$AudioSegment$from_wav('142533.wav')
#important: time.start and time.end must be integer
time.start <- as.integer(1*1000)
time.end <- as.integer(2*1000)
#create a slice object
sl<-pybuiltins$slice(time.start,time.end)
new.audio_split<-new.audio$`__getitem__`(sl)
new.audio_split
#<pydub.audio_segment.AudioSegment>

edited Mar 31, 2019 at 19:04

answered Mar 29, 2019 at 16:03

nicola

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