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Posts by Karl Knechtel
Understanding distutils and setuptools: the history The short version of "why does installing Setuptools fix the problem?" is that Setuptools provides its own distutils package, overriding anythin...
Sometimes when I try to install a third-party library for Python, I get an error saying that either distutils, or some part of it like distutils.core or distutils.util, could not be found. It's sho...
Starting up Python There are several key ways to use the python command from the command line: python by itself starts a REPL that allows typing in and running Python code on the fly, one sta...
Suppose I have some code in a file myscript.py like: def my_function(): print("Test") What steps do I need to take in order to make my_function run? That is to say: how do I get Python to ...
Generallly (assuming no exploit is found) it's not possible to escalate the privileges of an already running process, except via code that itself has kernel level access (running in ring 0 - this i...
The fundamental problem here is that it is already ambiguous where the "end" of the data in the buffer is. Strings can be empty (have zero length as reported by strlen); as such, buffer could equal...
This question is inspired by If I have a char array containing strings with a null byte (\0) terminating each string, how would I add another string onto the end? on Stack Overflow. Suppose I have...
No. Terms like "too generic", "unclear", "too broad", "off topic" are absolutely not euphemisms for "stupid question, go away". They mean what they say; and when they are used Somewhere Else, mult...
Theory Relative paths are relative to the current working directory of the Python process. This can be checked from within Python using the os.getcwd function and set using the os.chdir function. ...
The raise statement in Python accepts either an Exception class or an instance of that class. When used with a class, Python will create and raise an instance by passing no arguments to the constru...
Command-line timing Rather than using separate code for timing, I tried running the timeit module as a command-line tool. I wrote initial versions of the implementations based on the OP and hkotsu...
PEP 8 Four-space indentation is the community standard. There are many strategies for wrapping long lines; I have found that it's often best to just use temporary variables to avoid wrapping lines...
Root cause ModuleNotFoundError is a kind of ImportError. It occurs when Python code tries to use an absolute import, but can't find the named module - just as the name suggests. (Failed relative i...
A well-known easter egg in Python displays some ideas about writing good Python code, credited to Tim Peters (one of the core developers). This question is about the last: Namespaces are one hon...
How to do it Yes, Python has an equivalent operator. However, it's spelled with keywords rather than punctuation, and it uses a different order of operands. It looks like: condition_value if some...
Sometimes code needs to assign (or otherwise use) a value that depends on some condition. The naive approach is to use explicit branching, which in Python would look like: if some_condition(): ...
My actual motivation is to understand the semantics of the .gitignore file syntax in precise detail, for a program which is expected to emulate them as accurately as possible. However, while coming...
These two uses of if are different The if at the end of a list comprehension syntax: [num for num in hand if num != 11] is a filter; its purpose is to decide whether or not the resulting list ...
Possible justifications It may make sense to use a mutable default argument in the following situations: For simplicity Consider for example an argument that should be some kind of mapping, wher...
Workarounds Avoiding mutation Because problems are only caused by actually mutating the default argument, the simplest way to avoid problems is to... not do that. Pythonic code obeys command-quer...
Terminology "Mutable default argument" means exactly what the individual words would suggest: it's an argument which is supplied as the default value for that parameter, which also is mutable. To ...
Consider this code example: def example(param=[]): param.append('value') print(param) When example is repeatedly called with an existing list, it repeatedly appends to the list, as ...
Background This is inspired to some extent by https://software.codidact.com/posts/289597 . I'm trying to provide a large amount of content (gradually!) that novices (mainly to Python) will find u...
As the author, this is my defense. Design and modeling are on-topic The site topicality documentation explicitly includes "Software design, architecture, or modeling" as on topic. There doesn't s...
First store the universe of potential elements as a sequence, then encode each set as an unsigned integer interpreted as follows: if the 1s bit in binary is set (1), the set contains the 0th elemen...
