PosixPath error when loading schema

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Kyle Downey

Jun 1, 2021, 10:35:19 AMJun 1
to Cap'n Proto
I have the following simple schema:


enum Side {
buy @0;
sell @1;

struct TradeMessage {
time @0 : Float64;
tradeId @1 : Int64;
side @2 : Side;
size @3 : Float64;
price @4 : Float64;

struct Level1BookUpdateMessage {
time @0 : Float64;
best_bid_qty @1 : Float64;
best_bid_px @2 : Float64;
best_ask_qty @3 : Float64;
best_ask_px @4 : Float64;

which I am loading as follows using pycapnp 1.0.0 on MacOS 11.4 running Python 3.8:

import capnp

from pathlib import Path

capnp_path = Path(__file__).parent / '../../../../capnp/serenity-fh.capnp'
capnp_def = capnp.load(capnp_path)

It fails on load with the following error. Any ideas on what I might be doing wrong?

Connected to pydev debugger (build 202.6397.98)
Traceback (most recent call last):
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 783, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/Users/kdowney/dev/shadows/serenity/src/serenity/marketdata/fh/txlog.py", line 6, in <module>
    capnp_def = capnp.load(capnp_path)
  File "capnp/lib/capnp.pyx", line 4030, in capnp.lib.capnp.load
  File "capnp/lib/capnp.pyx", line 3276, in capnp.lib.capnp.SchemaParser.load
AttributeError: 'PosixPath' object has no attribute 'endswith'

Kenton Varda

Jun 1, 2021, 10:41:08 AMJun 1
to Kyle Downey, Cap'n Proto
Hi Kyle,

I think you need to convert `capnp_path` back into a string before passing it to `capnp.load()`. Currently it appears you are passing a `Path` object that you constructed using pathlib, but `capnp.load` doesn't know how to deal with those, it wants a plain string.


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Kyle Downey

Jun 1, 2021, 3:57:33 PMJun 1
to Kenton Varda, Cap'n Proto
Yep that was it. Casting via str() did the trick.
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