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:

  • logging_strict@programming.dev
    3·
    10 days 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·
      10 days 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
  • KindaABigDyl@programming.dev
    42·
    11 days ago

    Another reason why raw pointers are superior to object nonsense

    Isn’t “explicit is better than implicit” part of the Zen of Python?

    • logging_strict@programming.dev
      02·
      10 days ago

      Not everyone is a C or a Rust coder. In C, sending in a pointer, know it’s pass by reference, not pass by value.

      In Python, depends if it’s immutable or mutable. Python coders eventually become hyper aware of the difference.

      Python coders that want direct access to C libraries can use Cython CPython or ctypes. Probably missing a few options. Maybe others can chime in. This comes at the expense of much more complicated packaging.

      Any package author that has underlying C code in their package automagically gains rock star status.