submitted 6 months ago by bterwijn@programming.dev to c/python@programming.dev

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An exercise to help build the right mental model for Python data. The “Solution” link uses memory_graph to visualize execution and reveals what’s actually happening:

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[-] logging_strict@programming.dev 3 points 6 months ago

For those with:

ancient browsers that won't run that memory graph web debugger
the attention span of a pigeon and can't be bothered to read a long explanation that doesn't address this particular pycon


>>> import copy
>>>
>>> a = [[0]]
>>> c1 = a
>>> c2 = a[:]
>>> c3 = list(a)
>>> c4 = a.copy()
>>> c5 = copy.copy(a)
>>> c6 = copy.deepcopy(a)
>>> 
>>> c1[0].append(1)
>>> c2[0].append(2)
>>> c3[0].append(3)
>>> c4[0].append(4)
>>> c5[0].append(5)
>>> c6[0].append(6)
>>> 
>>> print(a)
[[0, 1, 2, 3, 4, 5]]

copy.deepcopy makes a separate memory copy into c6. So appending to c6 affects c6, but not a

[-] logging_strict@programming.dev 2 points 6 months ago

This is what i get when click Play button

Traceback (most recent call last):
  File "/lib/python3.12/site-packages/micropip/_commands/install.py", line 142, in install
    await transaction.gather_requirements(requirements)
  File "/lib/python3.12/site-packages/micropip/transaction.py", line 55, in gather_requirements
    await asyncio.gather(*requirement_promises)
  File "/lib/python3.12/site-packages/micropip/transaction.py", line 62, in add_requirement
    return await self.add_requirement_inner(Requirement(req))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/lib/python3.12/site-packages/micropip/transaction.py", line 151, in add_requirement_inner
    await self._add_requirement_from_package_index(req)
  File "/lib/python3.12/site-packages/micropip/transaction.py", line 186, in _add_requirement_from_package_index
    metadata = await package_index.query_package(
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/lib/python3.12/site-packages/micropip/package_index.py", line 286, in query_package
    raise ValueError(
ValueError: Can't fetch metadata for 'memory-graph'. Please make sure you have entered a correct package name and correctly specified index_urls (if you changed them).
Traceback (most recent call last):
  File "/lib/python3.12/site-packages/micropip/_commands/install.py", line 142, in install
    await transaction.gather_requirements(requirements)
  File "/lib/python3.12/site-packages/micropip/transaction.py", line 55, in gather_requirements
    await asyncio.gather(*requirement_promises)
  File "/lib/python3.12/site-packages/micropip/transaction.py", line 62, in add_requirement
    return await self.add_requirement_inner(Requirement(req))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/lib/python3.12/site-packages/micropip/transaction.py", line 151, in add_requirement_inner
    await self._add_requirement_from_package_index(req)
  File "/lib/python3.12/site-packages/micropip/transaction.py", line 186, in _add_requirement_from_package_index
    metadata = await package_index.query_package(
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/lib/python3.12/site-packages/micropip/package_index.py", line 286, in query_package
    raise ValueError(
ValueError: Can't fetch metadata for 'memory-graph'. Please make sure you have entered a correct package name and correctly specified index_urls (if you changed them).

From console

Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at https://static.cloudflareinsights.com/beacon.min.js/vcd15cbe7772f49c399c6a5babf22c1241717689176015. (Reason: CORS request did not succeed). Status code: (null).

None of the “sha512” hashes in the integrity attribute match the content of the subresource. The computed hash is “z4PhNX7vuL3xVChQ1m2AB9Yg5AULVxXcg/SpIdNs6c5H0NE8XYXysP+DGNKHfuwvY7kxvUdBeoGlODJ6+SfaPg==”. memory-graph.com
Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at https://static.cloudflareinsights.com/beacon.min.js/vcd15cbe7772f49c399c6a5babf22c1241717689176015. (Reason: CORS request did not succeed). Status code: (null).

None of the “sha512” hashes in the integrity attribute match the content of the subresource. The computed hash is “z4PhNX7vuL3xVChQ1m2AB9Yg5AULVxXcg/SpIdNs6c5H0NE8XYXysP+DGNKHfuwvY7kxvUdBeoGlODJ6+SfaPg==”. memory-graph.com
Content-Security-Policy: The report URI (about:blank) should be an HTTP or HTTPS URI. memory-graph.com
Content-Security-Policy: (Report-Only policy) The page’s settings would block a worker script (worker-src) at https://memory-graph.com/py_worker.js from being executed because it violates the following directive: “worker-src 'none'” memory-graph.com
Loading micropip, packaging pyodide.asm.js:10:95312
Loaded micropip, packaging pyodide.asm.js:10:95608
PythonError: pyodide.asm.js:10:52088