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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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 ...
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229 votes
9 answers
76k 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 ...
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208 votes
8 answers
276k 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 ...
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172 votes
23 answers
25k 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 ...
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154 votes
1 answer
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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?
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147 votes
24 answers
211k 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 ...
134 votes
15 answers
32k 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 ...
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132 votes
3 answers
60k 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?" ...
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115 votes
2 answers
113k 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 the ...
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  • 1,662
108 votes
10 answers
78k 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++, ...
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106 votes
8 answers
20k 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 ...
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103 votes
9 answers
27k 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 ...
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96 votes
5 answers
229k 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 ...
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93 votes
3 answers
110k views

Why is Python written in C and not in C++?

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 ...
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91 votes
5 answers
240k 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 ...
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89 votes
6 answers
13k 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 ...
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88 votes
5 answers
146k 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 = None ...
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87 votes
6 answers
110k 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 (""). ...
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85 votes
7 answers
23k 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 ...
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82 votes
5 answers
150k 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 ...
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82 votes
3 answers
41k 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 ...
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66 votes
6 answers
82k 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 ...
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60 votes
3 answers
95k 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 *...
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60 votes
5 answers
48k 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 ...
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60 votes
5 answers
110k 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 ...
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57 votes
6 answers
11k 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 ...
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57 votes
3 answers
112k 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?
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56 votes
16 answers
51k 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 &...
54 votes
4 answers
43k 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 ...
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54 votes
5 answers
34k 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 ...
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51 votes
5 answers
77k views

Should I really use all uppercase for my constants?

I am a Python programmer primarily who uses pylint for linting source code. I am able to eliminate all of the warnings except one: Invalid name for a constant. Changing the name to all caps fixes it, ...
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50 votes
8 answers
9k views

Why is the worst case for this function O(n^2)?

I'm trying to teach myself how to calculate BigO notation for an arbitrary function. I found this function in a textbook. The book asserts that the function is O(n2). It gives an explanation as to why ...
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48 votes
5 answers
70k 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): ...
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48 votes
6 answers
129k 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), ...
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47 votes
4 answers
9k 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: ...
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  • 1,173
46 votes
8 answers
21k 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 ...
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46 votes
5 answers
93k views

Is it considered Pythonic to have multiple classes defined in the same file?

In working with python for the first time, I've found that I end up writing multiple classes in the same file, which is opposed to other languages like Java, which uses one file per class. Usually, ...
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44 votes
11 answers
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 ...
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  • 842
43 votes
13 answers
11k 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 ...
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43 votes
7 answers
11k 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/...
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43 votes
3 answers
79k 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]] &...
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43 votes
4 answers
33k 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 ...
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41 votes
3 answers
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 ...
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41 votes
3 answers
85k 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 ...
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40 votes
6 answers
10k 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 ...
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40 votes
6 answers
33k views

Which style to use for unused return parameters in a Python function call

Is there any recommended/generally accepted coding style for handling situations where a function returns a tuple of values but only one of those values is used afterwards (note that this is mostly ...
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  • 511
40 votes
4 answers
16k views

@staticmethod vs module-level function

This is not about @staticmethod and @classmethod! I know how staticmethod works. What I want to know is the proper use cases for @staticmethod vs. a module-level function. I've googled this ...
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  • 1,173
39 votes
14 answers
384k 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 ...
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  • 589
39 votes
3 answers
15k views

Why are C++ template error messages so horrific?

C++ templates are notorious for generating long, unreadable error messages. I have a general idea of why template error messages in C++ are so bad. Essentially, the problem is that the error isn't ...
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  • 2,455
38 votes
5 answers
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 "...
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