assert os.path.isfile only working with full path - python

I've been given an educational assignment during which I write Gherkin scenarios to test a website using Python 3.6, Splinter and Behave. I'm making some pretty good progress but I'm stuck on this little thing. Currently I've succeeded in getting a file to download through a headless instance of Chrome in Ubuntu. However, for the last step of the scenario to pass, I need to verify the file's existence. After a lot of searching I've found a method that works, which is:
assert os.path.isfile('/home/[USERNAME]/Downloads/file.csv')
However, in order to make this test more compatible with other computers, I'd like the path to the file to be shorter and simpler. Most importantly, not using this system's username.
I'm new to all of this so this could very well be a dumb question, but I've been searching all over the place and I simply can't find an answer.

You could rewrite the path using the ~ which replaces /home/[USERNAME]/, so it would become ~/Downloads/file.csv. Then, you could use Python's os.path.expanduser() function as follows:
assert os.path.isfile(os.path.expanduser('~/Downloads/file.csv'))
os.path.expanderuser() will automatically expand it to /home/[USERNAME]/ for you.

If you need to get Downloads folder path, than you can use answer to this question: python - Finding the user's "Downloads" folder

Related

Does Pyinstaller's "runtime-tmpdir" parameter affects the performance of the exe?

I am creating a one file executable and curious about the runtime-tmpdir parameter. As the one file always creates temp files in OS temp dir whenever opened, I want to change that with this option. But I am a bit worried before using this parameter as in the docs of Pyinstaller it is mentioned- "Please use this option only if you know what you are doing".
Its a bit silly question but will it affect the performance or any other system files?
Personally, the mention didn't bother me. It should not affect performance, but it is possible for errors, depending on how your code is structured. I use "--runtime-tmpdir" and I'm fine :)

Is it possible to examine the inner statements of a function?

Working from the command line I wrote a function called go(). When called it receives input asking the user for a directory address in the format drive:\directory. No need for extra slashes or quotes or r literal qualifiers or what have you. Once you've provided a directory, it lists all the non-hidden files and directories under it.
I want to update the function now with a statement that stores this location in a variable, so that I can start browsing my hierarchy without specifying the full address every time.
Unfortunately I don't remember what statements I put in the function in the first place to make it work as it does. I know it's simple and I could just look it up and rebuild it from scratch with not too much effort, but that isn't the point.
As someone who is trying to learn the language, I try to stay at the command line as much as possible, only visiting the browser when I need to learn something NEW. Having to refer to obscure findings attached to vaguely related questions to rediscover how to do things I've already done is very cumbersome.
So my question is, can I see the contents of functions I have written, and how?
Unfortunately no. Python does not have this level of introspection. Best you can do is see the compiled byte code.
The inspect module details what information is available at runtime: https://docs.python.org/3.5/library/inspect.html

Incorrect path with function getcwd()

I get the wrong path back. The Datafile is in D:... and get everytime the path C:\Python27\lib\site-packages\xy back from python. I use the function
path = getcwd()
How can I fix it?
You may be executing the script in a different place than your intended directory.
Solution 1: Move the .py file to the target directory, and execute it there.
Pros:
Easy
Works cross-platform (and for other users - if you do this, use getcwdu for Unicode)
No hard-coded path strings
Cons:
File must be in the same or higher directory as target folder
Solution 2: Manually write the string of the path to the folder.
Pros:
'Just Works'
Cons:
Annoying bugs w/typos
Need to re-code every time you change directories
Won't work anywhere else
In my idea, make sure your IDE has your target directory opened as your project folder.
After all, it's a debug-time error, and won't affect the smooth running of your program in the runtime, if your program's launch script has the right address for your program to run, and does its part normally!
By the way #order, I'm totally against hardcoding a path into your code, because it's just a very lame programming exercise!
Just get yourselves used to going through the right exercise, although it doesn't seem very beneficial in the short run. in the coming years of your career, you're going to be against using the cons and pros of such a comparison, but it will become a right or wrong coding exercise!
Cheers.

Navigating a big Python codebase faster

As programmers we read more than we write. I've started working at a company that uses a couple of "big" Python packages; packages or package-families that have a high KLOC. Case in point: Zope.
My problem is that I have trouble navigating this codebase fast/easily. My current strategy is
I start reading a module I need to change/understand
I hit an import which I need to know more of
I find out where the source code for that import is by placing a Python debug (pdb) statement after the imports and echoing the module, which tells me it's source file
I navigate to it, in shell or the Vim file explorer.
most of the time the module itself imports more modules and before I know it I've got 10KLOC "on my plate"
Alternatively:
I see a method/class I need to know more of
I do a search (ack-grep) for the definition of that method/class across the whole codebase (which can be a pain because the codebase is partly in ~/.buildout-eggs)
I find one or more pieces of code that define that method/class
I have to deduce which one of them is the one I need to read
This costs a lot of time, which is understandable for a big codebase. But I get the feeling that navigating a large and unknown Python codebase is a common enough problem.
So I'm looking for technical tools or strategic solutions for this problem.
...
I just can't imagine hardcore Python programmers using the strategies outlined above.
on Vim, I like NERDTree (a file browser) and taglist.vim (source code browser --> http://www.vim.org/scripts/script.php?script_id=273)
also in Vim, you can use CTRL-] to jump to a definition (:h CTRL-]):
download exuberant ctags http://ctags.sourceforge.net/
follow the install directions and put it somewhere on your PATH
from the 'root' directory of your source code, make a tags file from the shell: "ctags -R"
(make sure you have :set noautochdir, and make sure :pwd is the root directory from step 3)
go into Vim, cursor over some function or class name, hit CTRL-]
by default, if there's multiple matches for the tag, it shows you everywhere it was imported, and where it was declared
if the tag only has one match, it immediately jumps to it
...then use Ctrl+O and Ctrl+I to move back and forth from where you were
(repeat above steps for the source code of particular libraries you use, i usually keep a separate Vim window open to study stuff)
I use ipython's ?? command
You just need to figure out how to import the things you want to look for, then add ?? to the end of the module or class or function or method name to view their source code. And the command completion helps on figuring out long names as well.
Try red pill: https://github.com/klen/python-mode

Using cscope to browse Python code with VIM?

Has anyone managed successfully using cscope with Python code? I have VIM 7.2 and the latest version of cscope installed, however it doesn't get my code's tags correctly (always off by a couple of lines). I tried the pycscope script but its output isn't supported by the modern version of cscope.
Any ideas? Or an alternative for browsing Python code with VIM? (I'm specifically interested in the extra features cscope offers beyond the simple tags of ctags)
EDIT: I'm going to run through the process step by step:
Preparing the sources:
exhuberant ctags, has an option: -x
Alternatively, ctags can generate a cross reference file which lists,
in human readable form, information about the various source objects
found in a set of language files.
This is the key to the problem:
ctags -x $(ls **/*.py); # replace with find if no zsh
will give you your database of source objects in a known, format, described under
man ctags; # make sure you use exuberant ctags!
Gnu Global is not limited to only the "out of the box" type of files. Any regular file format will serve.
Also, you can use gtags-cscope, which comes with global as mentioned in section 3.7 of the manual, for a possible shortcut using gtags. You'll end up with an input of a ctags tabular file which Global/gtags can parse to get your objects, or you can use the source for pycscope together with your ctags file of known format to get an input for the vim cscope commands in
if_cscope.txt.
Either way it's quite doable.
Perhaps you'd prefer idutils?
Definintely possible since
z3c.recipe.tags
on pypi makes use of both ctags and idutils to create tag files for a buildout, which is a method I shall investigate in short while.
Of course, you could always use the greputils script below, it has support for idutils , we know idutils works with python, and if that fails, there is also something called vimentry from this year that also uses python, idutils and vim.
Reference links (not complete list):
gtags vimscript, uses Gnu global. updated 2008
greputils vimscript, contains support for the *id idutils, 2005
lid vimscript, Ancient, but this guy is pretty good, his tag and buffer howtos are amazing 2002
An updated version of pyscope, 2010
Hopefully this helps you with your problem, I certainly helped me. I would have been quite sad tonight with a maggoty pycscope.
This seems to work for me:
Change to the top directory of your python code. Create a file called cscope.files:
find . -name '*.py' > cscope.files
cscope -R
You may need to perform a cscope -b first if the cross references don't get built properly.
From a correspondence with the maintainer of cscope, this tool isn't designed to work with Python, and there are no plans to implement that compatibility. Whatever works now, apparently works by mistake, and there is no promise whatsoever that it will keep working.
It appears I've been using an out-of-date version of pycscope. The latest version 0.3 is supported by the cscope DB. The author of pycscope told me that he figured out the output format for the cscope DB from reading the source code of cscope. That format isn't documented, on purpose, but nevertheless it currently works with pycsope 0.3, which is the solution I'll be using.
I'm going to accept this answer since unfortunately no other answer provided help even after bounty was declared. No answers are upvoted, so I honestly have no idea where the bounty will go.
There is a wonderful Python-mode-klen plugin. If you have it and rope (python refactoring library) installed, then going to the definition of a particular term is as simple as <C-c>g or <C-c>rag (first is filetype mapping, second is a global one). There are much more useful features, some useless for me. All of them are disableable. Features from list of questions found at cscope-intro:
Where is this symbol used? <C-c>f. Rather confusing though, as results in quickfix list do show - instead of the actual lines (though they point to the correct location). Maybe it will be fixed.
Where is it defined?, What is this global symbol's definition?, Where is this function in the source files? <C-c>g
What is <...> global symbol's definition? <C-c>raj
Not very much, but I am not too experienced user of ropevim.
I got the same question you got, after browsing the internet, I found a way to fix this:
create a python script: cscope_scan.py
import os
codeRootDir = os.getcwd()
__revision__ = '0.1'
__author__ = 'lxd'
FILE_TYPE_LIST= ['py']
if __name__ == '__main__':
import os
f = open('cscope.files','w')
for root,dirs,files in os.walk(codeRootDir):
for file in files:
for file_type in FILE_TYPE_LIST:
if file.split('.')[-1] == file_type:
f.write('%s\n' %os.path.join(root,file))
f.close()
cmd = 'cscope -bk'
os.system(cmd)
excute this script under you code's root folder, this will generate the cscope.files and then excute cscope -b I don't know what happens to my computer, the last two lines aren't working well, but I think manually type a cscope -bk is acceptable:)
This hack also seems to force cscope to go through Python files:
cscope -Rb -s *
If you accept that cscope is apparently not designed to work with Python.
Superset any language any tool question: How to find all occurrences of a variable in Vim?

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