Questions tagged [python]

Python is a dynamically typed, high-level interpreted programming 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 and exceptions, and has an extensive standard module library. Python is general-purpose and thus used widely, from the web to embedded systems.

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220
votes
9answers
70k views

Why do people hesitate to use Python 3?

Python 3 was released in December 2008. A lot of time has passed since then but still today many developers hesitate to use Python 3. Even popular frameworks like Django are not compatible with Python ...
169
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23answers
23k views

Programming cleanly when writing scientific code

I don't really write large projects. I'm not maintaining a huge database or dealing with millions of lines of code. My code is primarily "scripting" type stuff - things to test mathematical ...
147
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24answers
197k views

What are the drawbacks of Python? [closed]

Python seems all the rage these days, and not undeservingly - for it is truly a language with which one almost enjoys being given a new problem to solve. But, as a wise man once said (calling him a ...
140
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8answers
189k views

'import module' vs. 'from module import function'

I have always been using this method: from sys import argv and use argv with just argv. But there is a convention of using this: import sys and using the argv by sys.argv The second method makes ...
140
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1answer
94k views

Module vs. Package?

Whenever I do from 'x' import 'y' I was wondering which one is considered the 'module' and which is the 'package', and why it isn't the other way around?
133
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1answer
156k views

Python file naming convention?

I've seen this part of PEP-8 https://www.python.org/dev/peps/pep-0008/#package-and-module-names I'm not clear on whether this refers to the file name of a module/class/package. If I had one example ...
131
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15answers
28k views

Is it always a best practice to write a function for anything that needs to repeat twice?

Myself, I can't wait to write a function when I need to do something more than twice. But when it comes to things that only appear twice, it's a bit more tricky. For code that needs more than two ...
109
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3answers
51k views

Why Was Python Written with the GIL?

The global interpreter lock (GIL) seems to be often cited as a major reason why threading and the like is a touch tricky in Python - which raises the question "Why was that done in the first place?" ...
106
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10answers
77k views

Why is Python used for high-performance/scientific computing (but Ruby isn't)?

There's a quote from a PyCon 2011 talk that goes: At least in our shop (Argonne National Laboratory) we have three accepted languages for scientific computing. In this order they are C/C++, ...
98
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8answers
17k views

Are there any design patterns that are unnecessary in dynamic languages like Python?

I've started reading the design pattern book by the GoF. Some patterns seem very similar with only minor conceptual differences. Do you think out of the many patterns some are unnecessary in a ...
89
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2answers
81k views

What's wrong with relative imports in Python?

I recently upgraded versions of pylint, a popular Python style-checker. It has gone ballistic throughout my code, pointing out places where I import modules in the same package, without specifying ...
86
votes
9answers
23k views

Check First vs Exception Handling?

I'm working through the book "Head First Python" (it's my language to learn this year) and I got to a section where they argue about two code techniques: Checking First vs Exception handling. Here is ...
85
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5answers
206k views

Why is %s better than + for concatenation?

I understand that we should use %s to concatenate a string rather than + in Python. I could do any of: hello = "hello" world = "world" print hello + " " + world print "%s %s" % (hello, world) print ...
83
votes
6answers
12k views

Why was Python's popularity so sudden? [closed]

Python first appeared in 1991, but it was somewhat unknown until 2004, if the TIOBE rankings quantify anything meaningful. What happened? What caused the interest in this 13 year old language to go ...
79
votes
6answers
99k views

Single quotes vs double quotes [closed]

I just started a job where I'm writing Python after coming from a Java background, and I'm noticing that other developers tend to quote strings using single quotes ('') instead of double quotes (""). ...
79
votes
3answers
35k 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 ...
78
votes
8answers
104k views

Why use try … finally without a catch clause?

The classical way to program is with try ... catch. When is it appropriate to use try without catch? In Python the following appears legal and can make sense: try: #do work finally: #do ...
75
votes
5answers
139k views

Is Python Interpreted or Compiled?

This is just a wondering I had while reading about interpreted and compiled languages. Ruby is no doubt an interpreted language since the source code is processed by an interpreter at the point of ...
72
votes
7answers
18k views

How bad of an idea is it to use Python files as configuration files?

I've always used JSON files for configuration of my applications. I started using them from when I coded a lot of Java, and now I'm working mainly on server-side and data science Python development ...
68
votes
3answers
70k views

Why is Python written in C and not in C++? [closed]

In Python's tutorial one can read that Python's original implementation is in C; On the other hand, the Python implementation, written in C, (...) I'm very curious why was Python written in C and ...
68
votes
5answers
140k views

Why store a function inside a python dictionary?

I'm a python beginner, and I just learned a technique involving dictionaries and functions. The syntax is easy and it seems like a trivial thing, but my python senses are tingling. Something tells me ...
66
votes
5answers
98k 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 = ...
60
votes
5answers
107k views

R vs Python for data analysis [closed]

I have been programming for about a year and I am really interested in data analysis and machine learning. I am taking part in a couple of online courses and am reading a couple of books. Everything ...
59
votes
3answers
91k views

What is the name of ** in python?

When programming Python I sometimes do a ** to make a conversion. I understand what it does but what data structures am I manipulating? A dict and what is the other? An array? Is there a name for the *...
54
votes
16answers
50k views

Why such popularity with Python? [closed]

Other than being annoyed at whitespace as syntax, I'm not a hater, I just don't get the fascination with Python. I appreciate the poetry of Perl, and have programmed beautiful web services in bash &...
51
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6answers
9k views

Why aren't there other programming languages that compile to Python bytecode?

In Java, there are multiple languages that compile to Java bytecode and can run on the JVM -- Clojure, Groovy, and Scala being the main ones I can remember off the top of my head. However, Python ...
51
votes
4answers
55k views

Should I pass in filenames to be opened, or open files?

Suppose I have a function that does things with a text file - for example reads from it and removes the word 'a'. I could either pass it a filename and handle the opening/closing in the function, or ...
48
votes
4answers
32k views

Why do iterators in Python raise an exception?

Here's the syntax for iterators in Java (somewhat similar syntax in C#): Iterator it = sequence.iterator(); while (it.hasNext()) { System.out.println(it.next()); } Which makes sense. Here's the ...
48
votes
6answers
128k views

How do I learn Python from zero to web development? [closed]

I am looking into learning Python for web development. Assuming I already have some basic web development experience with Java (JSP/Servlets), I'm already familiar with web design (HTML, CSS, JS), ...
47
votes
5answers
36k views

Why doesn't Python allow multi-line lambdas?

Can someone explain the concrete reasons why BDFL choose to make Python lambdas single line? This is good: lambda x: x**x This results in an error: lambda x: x**x I understand that making ...
46
votes
5answers
47k views

Purpose of `return self` from a class method?

I came across something like this in an open-source project. Methods that modify instance attributes return a reference to the instance. What is the purpose of this construct? class Foo(object): ...
46
votes
8answers
20k views

How can I learn to effectively write Pythonic code?

Doing a google search for "pythonic" reveals a wide range of interpretations. The wikipedia page says: A common neologism in the Python community is pythonic, which can have a wide range of ...
45
votes
3answers
87k views

Why Python and not Lua? [closed]

Why has Python been backed by google and become so rapidly popular and Lua has not? Do you know why Lua has stayed in background?
43
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7answers
10k views

Are small amounts of functional programming understandable by non-FP people? [closed]

Case: I'm working at a company, writing an application in Python that is handling a lot of data in arrays. I'm the only developer of this program at the moment, but it will probably be used/modified/...
43
votes
4answers
6k views

Python Forgiveness vs. Permission and Duck Typing

In Python, I often hear that it is better to "beg forgiveness" (exception catching) instead of "ask permission" (type/condition checking). In regards to enforcing duck typing in Python, is this try: ...
41
votes
13answers
10k views

How does Python's handling of line-breaks differ from JavaScript's automatic semicolons?

Javascript has a feature called Automatic Semicolon Insertion where basically if the parser encounters an invalid token, and the last token before that was a line break, then the parser will insert a ...
41
votes
12answers
7k views

Is C# development effectively inseparable from the IDE you use?

I'm a Python programmer learning C# who is trying to stop worrying and just love C# for what it is, rather than constantly comparing it back to Python. I'm caught up on one point: the lack of ...
40
votes
6answers
8k views

Should I create a class if my function is complex and has a lot of variables?

This question is somewhat language-agnostic, but not completely, since Object Oriented Programming (OOP) is different in, for example, Java, which doesn't have first-class functions, than it is in ...
40
votes
3answers
5k views

Experience of Python's “PEP-302 New Import Hooks” [closed]

I'm one of the developers of Ruby (CRuby). We are working on Ruby 2.0 release (planned to release 2012/Feb). Python has "PEP302: New Import Hooks" (2003): This PEP proposes to add a new set of ...
39
votes
14answers
382k views

How is Python used in the real world? [closed]

I'm looking to get a job as a Python programmer. I know the basics of the language and have created a few games with it using pygame. I've also started to experiment with Django. However, looking at ...
38
votes
5answers
5k views

Java dev learning Python: what concepts do I need to wrap my head around?

Background: I've run through a few tutorials and written some small projects. All is going well enough using Google and StackOverflow. Several times in the last few days I've found myself wondering "...
38
votes
3answers
63k views

Why doesn't Python have a “flatten” function for lists?

Erlang and Ruby both come with functions for flattening arrays. It seems like such a simple and useful tool to add to a language. One could do this: >>> mess = [[1, [2]], 3, [[[4, 5]], 6]] &...
37
votes
3answers
70k views

What are “class methods” and “instance methods”, in Python?

There has been a discussion in chat relating to a question (the question itself being irrelevant to this one), that has revealed I may not know Python whatsoever. In my mind, although terminology ...
37
votes
3answers
28k views

Difference between a REPL and interactive shell

Noob question. I am not quite able to tell the difference between a REPL and an interactive shell just by reading the definitions on Wikipedia. Wiki notes that REPL is a particular kind of ...
35
votes
9answers
8k views

Is the algorithm more important than the programming language?

During the current (2013) Google Code Jam contest, there was a problem that took C++ and Java people 200+ lines of code as compared to Python people that solved the same problem only using 40 lines of ...
34
votes
4answers
5k views

Concrete examples of Python's “only one way to do it” maxim [closed]

I am learning Python and am intrigued by the following point in PEP 20 The Zen of Python: There should be one-- and preferably only one --obvious way to do it. Although that way may not be ...
32
votes
5answers
17k views

Are Python mixins an anti-pattern?

I'm fully aware that pylint and other static analysis tools are not all-knowing, and sometimes their advice must be disobeyed. (This applies for various classes of messages, not just conventions.) If ...
31
votes
6answers
14k views

Why does Python only make a copy of the individual element when iterating a list?

I just realized that in Python, if one writes for i in a: i += 1 The elements of the original list a will actually not be affect at all, since the variable i turns out to just be a copy of the ...
31
votes
4answers
11k views

Should I stick with or abandon Python to deal with concurrency?

I have a 10K LOC project written in Django with quite a deal of Celery (RabbitMQ) for asynchronicity and background jobs where needed, and have come to the conclusion that parts of the system would ...
31
votes
7answers
9k views

Functional programming compared to OOP with classes

I have been interested in some of the concepts of functional programming lately. I have used OOP for some time now. I can see how I would build a fairly complex app in OOP. Each object would know how ...