MATLAB gives error while running a good Python code: TypeError: 'float' object is not iterable

I am trying to run an averaging code that requires a list and a single number tau. The python code runs well in Python 3.5.3 with inputs for eg. average([[12,13,14],[24,26,28]],0.5). The python code is as follows:

from math import *
def average(spike_trains,tau):
    class Delta_error:
        def __init__(self,spike_trains,tau):
            self.n=len(spike_trains)
            self.big_train=[]
            for train in spike_trains:
                self.big_train=self.big_train + train
                #print(self.big_train)
                #self.big_train.append(train)
            self.centre_train=[]
            self.tau=tau
            self.min=min(self.big_train)
            self.max=max(self.big_train)

        def add_spike(self,time):
            self.centre_train.append(time)
            
        def minimize(self):
            value=1.0
            time=self.min

            for spike in self.big_train:
                new_value=self.__call__(spike)
                if new_value<value:
                    value=new_value
                    time=spike
            return time
            
        def sort(self):
            self.centre_train.sort()
            
    delta_error=Delta_error(spike_trains,tau)
    train_length=len(delta_error.big_train)//len(spike_trains)
     
    for spike_c in range(0,train_length):
        new_spike = delta_error.minimize()
        delta_error.add_spike(new_spike)
        
    delta_error.sort()
    return delta_error.centre_train

Answer: [13, 24, 26]. In python.

When running in MATLAB running Python 3.5.3 (from pyversion)

py.average.average([[12,13,14],[24,26,28]],0.5)

I get the following vague error:

Python Error: TypeError: can only concatenate list (not "float") to list

The bolded lines have been problematic in MATLAB, but after changing the version of python running in MATLAB, I am only getting a one line error.

I need this code to work in MATLAB. What should I do? I would appreciate all tips and suggestions!

[Kojiro Saito]

Could you show us "__call__" definition in your Python scripts?

[Ritwika Mukherjee]

This is not problematic so far. Here it is:

def __call__(self,time):

cross1=0.0

for centre_time in self.centre_train:

cross1+=exp(-fabs(centre_time-time)/self.tau)

cross2=0.0

for big_time in self.big_train:

cross2+=exp(-fabs(big_time-time)/self.tau)

return 1.0+2.0*cross1-2.0/self.n*cross2

Answer 1

[Kojiro Saito]

MATLAB needs to pass Python list and tuple data to your python class.

The followings work fine.

py.average.average(py.list({py.list({12,13,14}), py.list({24,26,28})}),0.5)
py.average.average(py.list({py.list([12,13,14]), py.list([24,26,28])}),0.5)

[Ritwika Mukherjee]

This worked! Thank you!

I was trying to use pylist before when I was trying to use a separate command structure:

EMGlist= py.list({py.list(m1.Ch2raster'),py.list(m2.Ch2raster')}); %that's my data in MATLAB

systemCommand=['python.exe average.py', EMGlist, 0.5] %python address, python code, %input arguments

system(sytemCommand)

This didn't work. I am not fully sure when py.list is needed and when it is not. Would you know why that is?

Again, thank you so much for fixing this!!!

[Kojiro Saito]

Here is an example of py.list for calling Python function from system command.

EMGlist= py.list({py.list([12,13,14]), py.list([24,26,28])});
systemCommand=['python.exe .\average.py ', '"', char(EMGlist), '" ', num2str(0.5)]; %python address, python code,                   %input arguments
[status,cmdout] = system(systemCommand)

Because system command (command line) allows characters but does not allow py.list, we need to convert py.list to characters and enclose those characters with single or double quotations.

Also, you need to add following codes in your python function in order to allow arguments from command line. This is a sample and might not be good-looking.

import sys
import ast

def average(spike_trains,tau):
# This part is same
#

if __name__ == '__main__':	
	spike_trains = ast.literal_eval(sys.argv[1])	
	tau = float(sys.argv[2])
	print(average(spike_trains, tau))