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Looking for a Python editor that will let me collapse functions

I really loved this feature when I used Eclipse for Java programming, but I can't find the same functionality for a Python editor. IDLE and Pyscripter are nice, but they don't help in this area.
Basically, I just want the option to collapse or otherwise hide functions that I don't feel like looking at for a while. Know of anything like this?

In addition to the aforementioned (great) editors, you might want to give PyDev a shot as well.

Geany can do this.

Notepad++ has this feature.

Komodo Edit IDE, for Windows, Mac and Linux, for Python, PHP, Ruby, JavaScript, Perl and Web Dev.

I've used Komodo Edit and Notepad++ in the past but my current preference is Sublime Text Edit 2.
Although not free (and actually quite expensive), it can be used in free mode with only an occasional reminder and no other restrictions.
It is actually written in Python so you get a Python console built in - you can also get other consoles such as JavaScript. It is VERY flexible & has some very good features. It is also has an excellent community with loads of very useful plugins.
It is much lighter on resource usage than Komodo, can use Textmate bundles directly (so gets loads of formatting options for different file types). It is cross-platform and doesn't even need installation on Windows.

Pycharm CE, from Jet Brains, indeed, wonderful. Functions and comments collapse is ready out of the box, as well as edit helpers. Project files and assets organization, integrated python console, powerful debugging tools,... Then, lots of plugins: git integration, tinycode view, extra languages' helpers and highlighters,.... anything you need when coding, but simple and easy to use. There's a Pro (paid) version for those who want even more.
https://www.jetbrains.com/pycharm/download
(This question is more than 10 years old. I got surprised, nobody answered about Pycharm before...)

compiling python code from gedit

I am using WinXP.
I am using gedit (2.30.1) as python IDE. But I don't how to compile my code from inside the gedit. I've searched the net, but can't found any good solution.

First of all, you don't compile a python code. Python's code is interpreted.
EDIT:
gedit doesn't come by default with the plugins necessary to do the development. You will have to install them. Look in the comment for the link.
You can also checkout a blog link.

Using any simple text editor won't give you much flexibility in running the code right from the application. Unless you add a few plugins here and there to gEdit, you couldn't do it natively from Linux either.
If you're keen on sticking with gEdit for your needs, then you would have to install the plugins in your system - here is a link that may be of use to you. If you're fine with moving to another text editor, then I would strongly recommend Geany, which does the same thing as gEdit, but is more fully-featured, and can allow for execution of code in the same application.

You almost never need to compile Python code, although sometimes, as a optimization, Python code could be transfered into C code for a higher performance with certain plugins. Python code are translated to *.pyc and run in a PVM.

Debugging Python code in Notepad++

I use Notepad++ for writing and running Python scripts. It is a great text editor, except for debugging. Is there a way to step through the code, use break points, view variable values etc. in Notepad++ like you can in Visual Studio?

Does such a plug-in exist? Not that I know of. I agree completely with qor72 on that note.
Is it possible to create such a plugin / functionality? Possibly.
After doing some quick digging, I did find a plugin that looks promising, Python Script. In short it allows you to run python scripts that can access the NPP modules (file menus etc...) as well as the Scintilla Methods which appear to give access to things like the markers on the pages.
To accomplish such a feat I could see the task being broken into a few large blocks (I feel a new open-source project coming on...)
Using Python Script, integrate the python debugger(PDB) as mentioned by Shashi.
Using the Scintilla Methods, add trace back calls where a NPP marker is placed
Redirect PDB outputs and process them to show where the file is stopped (again using the Scintilla methods).
While at the newly created breakpoint and using PDB determine all of the variables in the current namespace. Take this info and dump it to a CMD window, or if you want to get fancy some GUI created with Tk / wxPython
Closing Thoughts
While I think it's possible to create such a plug in, it would be quite an undertaking. Along that line, you might be better off trying to find a different editor that has this built into it already and just create macros (or whatever the IDE calls them) to add in the things you like most about NPP.
Please note that I am a daily user of NPP and have been for many years so I definitely understand why you'd like to have the functionally added to NPP. One of my favorite things about NPP is the speed in which it opens and searches files... moving to a bloated IDE, IMO, would not be worth it to me.
My current work flow is to do all of my editing in NPP and just double click to run the modules. If it fails or goes off in the weeds, I launch IDLE to debug it.

I really hope someone tells me I'm wrong (I'd love to have that feature in Notepad++) but, Notepad++ is designed as a programmers editor, not an IDE. While it has a lot of cool functionality, that level of debugging isn't part of the core tool.
Not seeing anything in the npp-plugins either.

I think python debugger
is the best option if editor is not providing facility :)
Quick guide:
from pdb import set_trace as bp
code
code
bp()
code
code
At the (Pdb) prompt, enter s to step, p foo to print foo, and c to continue executing the code until hitting another breakpoint.

Have you thought of using Komodo.
It's open source and has ports for Windows, Linux and MAC (I think).
This may be an alternative, and if you want some advice from notepad++ users, have a look at the following post on this very site:
Komodo Edit and Notepad++ ::: Pros & Cons ::: Python dev
Some npp users here seemed to have made the switch for python editing running etc...
personally don't know much about debugging on Komodo but as it's an IDE so would be surprised if you couldn't do it easily

I don't really see why Shashi's answer hasn't been upvoted. For the link that he has given supplies a way to step through python scripts as the OP has requested.
So for all who don't know about the pdb module, upon importing it the pdb.set_trace() function allows one to step through the area of code after it. And it is very much similar to the visual studios method of debugging. While you're stepping through the code you are able to input a variety of commands.
One of them is p <expression> and that allows the user to print the current state of variables within the local and global scope.

I know it's 11 years on, and I'm a bit late to the game, and I know it's not Notepad++ but please do consider Visual Studio Code.
It's free, easy to install (both the editor itself plus any python interpreters it uses) and it's widely used and nowhere near as bloated as it's Visual Studio counterpart. It also appears to be the IDE of choice for a lot of Cisco-related course material.
Write your code, click to the left of code pane to insert your breakpoints click the Debugger icon (highlighted), and you're away:

Autocompletion in dynamic language IDEs, specifically Python in PyDev

I'm new to Python, with a background in statically typed languages including lots and lots of Java.
I decided on PyDev in eclipse as an IDE after checking features/popularity etc.
I was stunned that auto-complete doesn't seem to work properly for builtins. For example if I try automcomplete on datafile after:
datafile = open(directory+"/"+account, 'r')
datafile.
No useful methods are suggested (e.g. realines). Only things like call.
I am used to learning a language by jumping into class definitions and using lots of auto-complete to quickly view what a class will do. My PyDev 'interpreter' is set up fine with 'forced builtins'.
Is it possible to get auto-complete for builtins with PyDev? Am I approaching the IDE wrong, i.e. should have an interpreter running on the side and test stuff with it? So far the IDEs have seemed weak, e.g. IDLE segfaulted on my new mac after 2 minutes. I'd love to know what experienced Python developers do when exploring unfamiliar (builtin) modules, as this is making me reconsider my initial attraction to Python. I like a language you can learn by easy exploration!
Thanks,

In my opinion, the Python shell is a much better place to explore new modules than relying on an IDE. Don't forget, in Python you can do anything in the shell that you can do in a program, because there's no separate compilation step. And in the shell, you can use dir(x) to find all the properties and methods of x, whether x is a module, a class, or whatever.
Even better, the enhanced iPython shell does provide tab completion for all objects.
In fact because of this, many Python programmers - myself included - don't use an IDE at all, but just a simple text editor (I use VIM).

Just to keep it up to date so that new readers are not confused about the current state of Pydev - the example you gave now works in Pydev. (btw, one should avoid operating on paths manualy - use os.path.join instead)

I'd love to know what experienced
Python developers do when exploring
unfamiliar (builtin) modules
I use ipython. Ipython is an enhanced version of the interactive shell that adds tab completion and quick access to an object's doctstring. It also gives lots of other features that the standard shell does not have - you can find a summary of its features here.

Someone more knowledgeable here can give you a detailed answer. Here is a short one.
Autocomplete for a dynamically typed language can by nature never be as rich as that for a statically typed language. In the case of open for instance there is no way to figure out what will be the return type at the time of writing the code. The method signature does not include a return type unlike a statically typed language like Java. Consequently the IDE is not able to give you any hints.
You certainly should have an REPL running during any Python development. One advantage of an interpreted language is that you can test small chunks of your code on the REPL as you go along. It is also a good place to test your understanding of how built-ins and other modules work.
I work on Ubuntu so I do not know how easy or difficult it is to get IDLE running on a Mac. I usually work with the very handy iPython for REPL needs and use Pydev for other development (such as Django). You might want to give iPython a try.

You want IPython. As Daniel pointed out above, the interactive shell is a much better way to explore Python (and indeed, most other languages too).
This might help with setting it up on OSX.

You might want to take a look at WingIDE. It autocompletes your datafile correctly.
If it is unable to infer the type, you can use an assert like
assert isinstance(datafile, file)
to help the autocompleter out

I use PyDev at work so I know where you're coming from. If you're willing to consider other tools, have a look at JetBrains' PyCharm, that's my new preferred Python IDE for my own projects. No affiliation to speak of except to say I'll be picking it up when it's out of beta. :)

How do I prepare myself for a summer of working on Python using Linux environment?

I have used just Windows for programming so far. Now, I have an internship starting in two weeks and I will be using just Linux environment with Python programming language. I've installed Ubuntu on my system but have no exposure to shell scripting.
I need some advice on how I can quickly learn to use the Linux terminal quickly. Any books or web resources that you can suggest?
Also, is there a particular IDE that is generally preferred for Python programming on Linux, or is Vim preferred? How can I best prepare myself for the internship ahead?
Thanks for taking the time.

As an intern you'll want to use the tools your mentor is most comfortable with. If you get stuck you'll be able to ask for advice quickly.
Learning your way around either vi, vim, or emacs to start with will help. The basic concepts used in one will transfer to the other. You'll need to be able to open and read files, search through files, edit and save files, and learn how to apply any python formatting helpers correctly.
You should also familiarize yourself with version control if you haven't already. Again any one will do, you need to focus on concepts and etiquette rather than the specific tool.
The goal of the internship (and really your entire time at university) should be used to learn concepts rather than specific tools. If you learn the concepts you'll be well placed to apply those concepts using any tool. You will also "learn how to learn" a new tool, which is really valuable.

Your lack of shell scripting knowledge shouldn't matter in this case, although it won't be hard to learn. I read over some shell tutorials and put them into practice. Try doing everything from the command line, including find (grep), find/replace all (sed), finding files (find), automating things using python scripts etc. Basically, don't cheat. You'll pick up a lot this way. You'll also probably end up wondering how you ever managed with Windows.
What I use depends on the project. I really like Eclipse+PyDev but that's my personal preference, I also use Vim depending on where I am/what I'm doing. Remember you can just type python from the command line and it drops you into the python environment.

I recommend Eclipse + PyDev too. You can get started quickly with this develop environment. I also recommend the website Dive Into Python. It provides you a online free version of Dive Into Python book, which is very easy to read, easy to understand, and very suitable for Python beginners. If you really want a paper book at hand, Learning Python, a.k.a. The Animal Guide, is simply the best.

Learn to understand man(ual) pages.
For almost any old linux command/program there is a man page which usually explains the command in good detail.
So basics for filesystem navigation:
Show directory contents (list)
ls
Show hidden files
ls -a
Show details
ls -l
Change directory
cd /full/path/name
Print current directory
pwd
Delete a file
rm file
Delete a directory (recursive)
rm -r directoryName
Make a directory
mkdir directoryName
Move (or rename) a file
mv /path/to/file /new/path/to/file
Show the man page for mv
man mv
Learning vim might be necessary, depending on your intern environment. I do my Python (and everything that isn't simple text editing) in Eclipse. You should in any case learn enough to open a file, makes some changes and save the changes in Vim.
Keep in mind, Ubuntu is very easy. To make things harder on yourself, use the command line for every conceivable thing. Open programs by typing their names into a terminal. Browse your files with the terminal. Do simple editing with vim. That should provide good practice for the day you need to SSH into a computer in Neverland and download and install a local copy of your favorite interpreter from source in order to set up a cron job to run a script to play a clock noise.

In addition to the great advice already written, I'd suggest you install IPython (Open a terminal with Applications>Accessories>Terminal and type):
sudo apt-get install ipython
Also at the terminal, you can then type ipython to start the Python interpreter.
Unlike the built in python interpreter, ipython gives you tab completion.
For example, if you type the name of an object followed by a period and TAB (e.g. sys.[TAB]), ipython will show you (almost) all of object's attributes.
Type a question mark after an object name (e.g. sys?), and you get documentation on that object.
This is a great way to explore Python.

have no exposure to shell scripting
Good! You've got Python so hopefully there should be no need to resort to writing actual scripts with the shell. It may be more powerful than DOS batch files, but it's just as ugly.
I need some advice on how I can quickly learn to use the Linux terminal quickly.
Something like this?
As well as learning the commands, you'll want to get used to using tab-completion and arrow key command recall (if you don't already do that with the Windows Command Prompt), scrolling with shift-arrows, and so on. Also useful to know the & (perform in background) command suffix, ctrl-C-to-stop, ctrl-Z-to-pause, jobs, and screen.
Incidentally if you will be spending any amount of time in the interactive Python interpreter it is well worth adding tab completion there, too. (This is just as much the case on Windows, but on Win you tend not to get pyreadline by default.)
is there a particular IDE that is generally preferred for Python programming on Linux
Just like on Windows, there are IDEs available if you want them but many people just use a normal text editor. vim is fine if that's what you like. nano is another in-terminal text editor you usually get that's relatively simple. Ubuntu's default desktop-based editor gedit is also fine. It's a matter of personal taste.
(If you are interning at a particular company they might have their own development environment they'd prefer you to use.)

For a Python IDE, I recommend using either IDLE or Eclipse with PyDev.
Keep in mind you can also just use python on the linux command-line. It supports loading code from files, and if you use two command windows then one of them will be your "REPL" where you will be running python and dynamically loading code - and the other window can run your editor.
Regarding linux command line, I cannot recommend any great resources. However, you will be off to a great start if you immerse yourself in this environment and only use linux for the next 2 weeks. Just keep learning, and when you do not know how to do something, read a manpage or google it to find the answer.

for a very beginner intro to the command line, check out: http://en.flossmanuals.net/CommandLineIntro/GettingStarted

As far as a Python editor goes, I personally prefer to use SciTE. It's just a programmer's text editor with syntax highlighting for various languages. I prefer a lightweight editor over a more complicated environment, but if you want a full-fledged IDE you can always try out NetBeans, IDLE, or Komodo (all of which are available in both Windows and Linux).

as for terminall and quick way to understand it's and learn it there are a nice cheat sheets on net like this:
http://fosswire.com/post/2007/8/unixlinux-command-cheat-sheet/