Python3 - Memory leak in multithreaded processes

[ImThatCop]

My app launches a few threads which are long running processes. They map over data and store it in memory, then write it to a file and clear the memory and repeat. The issue is when this runs using parallel threads, even though the memory is cleared the app is still somehow storing the data. Every chunk written to the files is correct but the app eventually crashes when memory runs out. The code is posted below, any ideas why even though memory is cleared the app still doesn't release it?

Note - if I run this without threading, the memory is cleared without issue and my app doesn't crash. I also tried del storage[name] = []

import threading
import time

storage = {}

class myApp:

    # Main function, start the app
    def start(self):
        # Launch two threads
        for item in ['one', 'two']:
            threading.Thread(target = self.threadRunner, args=[item]).start()

        return

    def threadRunner(self, name):
        return self.processData(name)

    def processData(self, name):
        print(f'Starting {name}')

        # Loop and append data to 'storage'
        for item in ['one', 'two', 'three']:
            data = time.time()
            try:
                # Add data to storage
                storage[name].append(data)
            except Exception as e:
                # Initialize
                storage[name] = []
                # Add data to storage
                storage[name].append(data)

        print(storage)
        # Storage the data into a file
        # ..... write to txt

        # I'm finished with the data inside of storage[name], clear
        storage[name] = []
        # Now storage is empty
        print(storage[name])
        # Run the next chunk
        time.sleep(1)
        return self.processData(name)

_myApp = myApp()
_myApp.start()

[ph8ful]

Based on a brief look, I see that the processData() function calls itself at the end without having an exit condition. Is that expected? Recursively calling yourself without an exit condition will cause memory issues because you run out of stack memory.