Object serialization / saving an object to filesystem?

[IcedRooibos]

Is there any recommended/general purpose way to save objects to the filesystem at the moment? Or should I go ahead and write custom code based on how my particular objects are structured?

Here's a very basic example to show what I'd like to do

class refObj():
    def __init__(self, v1, v2, v3, v4, rObj=None):
        self.var1 = v1
        self.var2 = v2
        self.var3 = v3
        self.var4 = v4
        self.rObj = rObj
    def doStuff(self):
        print(self.var1+self.var2+self.var3+self.var4)
        if self.rObj != None:
            self.rObj.doStuff()

        
a = refObj(1,2,3,4)
b = refObj(5,6,7,8,a)
c = refObj(9,10,11,12,b)

# Save above objects to filesystem to use later (in practice they
# will be defined through user input)

# write object to a file
# How?

# Stuff happens, power loss etc
del a
del b
del c

# Load above objects on startup
# How?

a.doStuff()
b.doStuff()
c.doStuff()

[cve2022]

What about json?

[brave-ulysses]

https://pypi.org/project/micropython-pickle/

[IcedRooibos]

@cve2022

Thank you! I tried to use json.dumps on object.__dict__ but it doesn't handle recursion natively i.e. another object is part of object.__dict__. This means I would have to write custom code to handle that. I just asked this question to make sure that I wasn't missing some library that was already written and tested.

@brave-ulysses

Thank you, I did see that earlier but unfortunately it looks like it's not developed yet.

From the link:
This is a dummy implementation of a module for MicroPython standard library. It contains zero or very little functionality

[bixb922]

A updated version of pickle is in micropython-lib (https://github.com/micropython/micropython-lib/tree/master/python-stdlib/pickle).

[IcedRooibos]

That's awesome, thank you @bixb922!

[peterhinch]

This doc lists several options for serialisation with the benefits and drawbacks of each.

[IcedRooibos]

Thank you!