Python is a dynamic, high-level language. Its design focuses on clear syntax, an intuitive approach to object-oriented programming, and making the right way to do things obvious. Python supports modules, exceptions, had an extensive standard module library. Python can also be embedded in other ...

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2
votes
0answers
52 views

Breaking a table over multiple lines in Sphinx

Lets say I have the following function with a docstring: def foo(*args): """ do some fooness +----------------------------+----------------------------------------------------+ | ...
4
votes
4answers
661 views

How to rotate an array of bits

I currently have a PIL Image object which I store as an array of bits (1's and 0's). However I now would like to be able to rotate that image 45 degrees. One way to do it is take the original PIL ...
2
votes
1answer
146 views

What exactly is this Python statement doing?

I'm trying to port a very basic dual contouring algorithm written in Python (here) to C++. I'm not a Python programmer so some of the language syntax is a bit foreign to me. Specifically, this block ...
-3
votes
2answers
54 views

How to perform deferred tasks in backend [closed]

Actually the problem is very common. Let me describe this by example. Imagine you have a web service where users register and pay for some gold status. There is expiration date. The question is how to ...
1
vote
4answers
451 views

How to clean up nested try/except/else?

When writing code, I often want to do something like this: try: foo() except FooError: handle_foo() else: try: bar() except BarError: handle_bar() else: ...
0
votes
3answers
152 views

Is this a pattern: stand-alone classes

Having recently discovered python, I attempted to write a simple logger. Data is read from a device, processes, displayed and stored on disc. Those different tasks belong to different modules, of ...
0
votes
1answer
182 views

Is there a way to prevent variables from changing their type in Python?

It is useful to have the interpreter derive the type of a variable automatically. This on its own is similar to the auto keyword in C++11. However, in Python variables can change their type after ...
1
vote
2answers
170 views

Is using os.environ to store the value of command line switches pythonic?

I write CLI-executable Python 3 scripts regularly to do data compilation and some maintenance tasks, and try to adhere to PEP 8 and the Google Python Style Guide when doing so. Google's guide says to ...
0
votes
1answer
92 views

Checking that a function is only run from __main__ in Python

I often end up with code files that can either be imported or run as __main__. It's easy to handle this by checking if __name__ == '__main__'. But sometimes if my main function gets too big I split ...
0
votes
0answers
34 views

Advice on which approach to follow for sandboxing the input in an intentional “vulnerable” web app (sandbox in python) [duplicate]

my question is about which is the best approach/practice on building a "sandbox mechanism" in Python in a web application. The app will provide intentional vulnerable scenarios, and the user has to ...
13
votes
4answers
4k views

Best practices for execution of untrusted code

I have a project where I need to allow users to run arbitrary, untrusted python code (a bit like this) against my server. I'm fairly new to python and I'd like to avoid making any mistakes that ...
4
votes
3answers
534 views

How to avoid large function arity / exposure of underlying implementation

Currently reading Clean Code, and the authors seem to imply that any function with an arity greater than 3 should be avoided at all costs. I am unfortunately running into an issue where I am faced ...
0
votes
2answers
112 views

Prime symbol in Python variable name

So I'm a terrible person and I want to name a variable in my mathy-python3 code s′ (that's a prime symbol). I was under the impression Unicode literals work as identifiers in Python 3, which is why ...
1
vote
2answers
112 views

Function has two sets of arguments, the latter of which calls a nested function? [closed]

The function foo, has a nested function; bar. Calling foo with a second set of arguments feeds them into bar if bar is returned at the end of foo. How does this work and what is it called? Are there ...
0
votes
0answers
82 views

Functional dependencies diagram

I'm searching for the correct type of diagram in which I can see all dependencies between the functions, classes and files of my Python program (multiple files). It's for cleaning purposes. So my ...
4
votes
6answers
341 views

Should I store x,y coordinates as an array, a class object, or two variables?

I have a MyObject which has an x and y coordinate. as far as I can see, I can store it in three ways: class MyObject: def __init__(self, x, y): self.x = x self.y = y class ...
-2
votes
1answer
212 views

Base Class, with method that returns Derived Class. design flaw?

I'm writing a Math equation solver in python (for fun). The first design that came to my mind: Expression: base class for every item in an equation (maybe bad name). BinaryExpression extends ...
9
votes
4answers
1k views

When and how should I use exceptions?

The Setting I often have trouble determining when and how to use exceptions. Let's consider a simple example: suppose I am scraping a webpage, say "http://www.abevigoda.com/", to determine if Abe ...
-1
votes
2answers
4k views

Visual web page designer for Django? [closed]

I'm just starting my Django learning so pardon me if any part of this question is off-base. I have done a lot of web searching for information on the equivalent of a visual web page designer for ...
0
votes
2answers
143 views

Need help understanding a recursion example in Python

Python is my first programming language, and I'm learning it from "How to Think Like a Computer Scientist". In Chapter 5 the author gives the following example on recursion: def factorial(n): if n ...
3
votes
3answers
425 views

Lambda expressions with no parameters in Haskell and / or lambda calculus

In eager languages like Scheme and Python, you can use a lambda expression without parameters to delay evaluation, e.g. in Scheme (Chicken Scheme): #;1> (define (make-thunk x) (lambda () (+ x 1))) ...
0
votes
1answer
69 views

Should instance variables be bound to the instance right in the beginning of the method they are created in?

A common problem for me - and it's not really a problem, but somehow I again and again ask myself, what is the normal way to handle this - is that there is a method and within this method a couple of ...
2
votes
1answer
76 views

Python property best practices [closed]

Is there any situation where it makes sense to define a python property, where getting (not setting) it would raise an exception? I don't think this ever happens for fields in classes, hence the ...
1
vote
1answer
99 views

writing functional/integration tests for python

I am new to python and functional/integration tests as a whole. I know how to write unit tests, but in this case i do not need isolation for specific functions, rather i need my python script to be ...
3
votes
2answers
183 views

Is a bad practice create database structure on the runtime?

Im creating a crawler app that will always in the beggining, when the Class constructor, ensure that the basic database structure exists. Is this a bad practice? What is the advantage os creating the ...
-1
votes
1answer
286 views

How do I create every permutation [closed]

I have a list of letters, this is just an example list: ['a','b','c','d','e'] How do I compute every combination of the list? The letters cannot repeat, for example. a,b,c,d,e a,c,b,d,e a,c,d,b,e ...
16
votes
8answers
1k views

What are good unit tests to cover the use case of rolling a die?

I'm trying to get to grips with unit testing. Say we have a die which can has a default number of sides equal to 6 (but can be 4, 5 sided etc.): import random class Die(): def __init__(self, ...
-1
votes
1answer
144 views

Unevenly distributed random number generation [duplicate]

Let's say I have to generate random number from 1 to 100, however, the probability of each number is not 1/100, but a predefined probability. How to generate that number? I use Ruby/Python.
2
votes
2answers
620 views

One boilerplate class or many similar classes?

Lets say I'm trying to model a variety of objects that are virtually identical, the only difference being their class variables. Am I better off creating one boilerplate class and just calling the ...
1
vote
4answers
125 views

Efficient “Object with weights” structure

I need to find an "efficient" data structure / set of algorithms to do the following things: I have a list of objects. I need to assign them weights and later on increase or decrease these weights. ...
3
votes
1answer
170 views

What is the right way to process inconsistent data files?

I'm working at a company that uses Excel files to store product data, specifically, test results from products before they are shipped out. There are a few thousand spreadsheets with anywhere from ...
0
votes
2answers
134 views

At what point should you start putting functions in a new file? [closed]

I'm currently writing a python script. It's currently about 400 lines long, and it seems like it's getting a bit long, as when I'm trying to scroll through it with eclipse it takes a bit to get from ...
1
vote
2answers
594 views

What is the proper name for this design pattern in Python? [closed]

In Python, is the proper name for the PersonXXX class below PersonProxy, PersonInterface, etc? import rest class PersonXXX(object): def __init__(self,db_url): self.resource = ...
7
votes
3answers
322 views

Does it make sense to develop open source python library for database inspection? [closed]

Some time ago I came up with an idea for a library for database inspection. I started developing it and got some very basic functionality, just to check if that's possible. Recently however, I get ...
7
votes
6answers
2k views

Python mutable default argument: Why?

I know that default arguments are created at the function initialisation time and not every time the function is called. See the following code: def ook (item, lst=[]): lst.append(item) ...
4
votes
3answers
913 views

What's the best way to create a static utility class in python? Is using metaclasses code smell?

Ok so I need to create a bunch of utility classes in python. Normally I would just use a simple module for this but I need to be able to inherit in order to share common code between them. The common ...
14
votes
5answers
3k views

Is it a good practice to declare instance variables as None in a class in Python?

Consider the following class: class Person: def __init__(self, name, age): self.name = name self.age = age My coworkers tend to define it like this: class Person: name = ...
3
votes
2answers
210 views

Which programming idiom to choose for this open source library?

I have an interesting question about which programming idiom is easier to use for beginner developers writing concrete file parsing classes. I'm developing an open source library, which one of the ...
1
vote
2answers
197 views

Is creating and writing to one large file faster than creating and writing to many smaller files in Python on Linux?

If using Python on a Linux machine, which of the following would be faster? Why? Creating a file at the very beginning of the program, writing very large amounts of data (text), closing it, then ...
37
votes
2answers
4k views

How do I move away from the “for-loop” school of thought?

This is a rather conceptual question, but I was hoping I could get some good advice on this. A lot of the programming I do is with (NumPy) arrays; I often have to match items in two or more arrays ...
0
votes
3answers
163 views

How to convert this recursive problem to iterative? Line Simplification algorithm fails to run due to Maximum Recursion Depth being hit

I am implementing the Douglas, Peucker's Line Simplification algorithm in Python. I started with this implementation. However, it fails to run in Python due to Maximum Recursion Depth being hit. How ...
4
votes
4answers
991 views

How does Python compile some its code in C?

I read that some constructs of Python are more efficient because they are compiled in C. https://wiki.python.org/moin/PythonSpeed/PerformanceTips Some of the examples used were map() and filter(). I ...
17
votes
9answers
5k views

Why hasn't C# gained much traction within the opensource community? [closed]

I'm not expecting C# to be on par with say Java or Python in the open source community, but it still surprises me just how far behind it is. 'Multi language' open source repos like google code or ...
0
votes
1answer
171 views

Best Practices For Temporary Scripts (Python)

I am running two separate programs which are similar enough that they share a lot of code. I run these programs often and after I evaluate the output. This is a very fluid process and everytime is ...
9
votes
5answers
987 views

Are there technical limitations or language features that prevent my Python script from being as fast as an equivalent C++ program?

I'm a long-time Python user. A few years ago, I started learning C++ to see what it could offer in terms of speed. During this time, I would continue to use Python as a tool for prototyping. This, it ...
3
votes
2answers
143 views

Should I use nested matrices or dictionaries?

As per Should I ask my question about which data structure to use here? I'm asking this here. Hopefully this isn't too implementation specific. I'm currently developing a program that will represent ...
1
vote
3answers
206 views

How do I test my code in Python other than by doing it by hand?

I am used to user testing in Java, and I also manually test each section of code I write, but now, I want to automate it. There is no GUI for this project, so user testing is not required and I can ...
0
votes
1answer
63 views

Where to save something between invocations?

The 2nd time I run this program I'd like it to start in the same HDD location as the previous instance. How should I save, or remember, where I was so the program starts in the same place? I'd like ...
2
votes
1answer
269 views

How do you make decorators as powerful as macros?

Quick background: I am designing a Pythonic language that I want to be as powerful as Lisp while remaining easy to use. And by "powerful", I mean "flexible and expressive". I've just been introduced ...
0
votes
1answer
157 views

Python case statement? [duplicate]

I made a simple Python script that takes user input in order to generate a series of mathematical responses. In one part I did this: while True: And iterated through the loop until I used an if ...