Reading/Writing files

[Jon Herman]

Folks,

thanks for the many responses! Specifying the full file name (and not using
parentheses when inappropriate, thanks Jack :)) I am now happily
reading/writing files.

My next question: what is the best way for me to write an array I generated
to a file?
And what is the best way for me to load that array again, the next time I
start up my computer?

Basically I am doing very large computations and want to store the results.

Thanks a lot guys!

Jon




On Fri, Mar 18, 2011 at 4:18 PM, Dan Stromberg <drsalists at gmail.com> wrote:

>
> Are you on windows?
>
> You probably should use / as your directory separator in Python, not \.  In
> Python, and most other programming languages, \ starts an escape sequence,
> so to introduce a literal \, you either need to prefix your string with r
> (r"\foo\bar") or double your backslashes ("\\foo\\bar").
>
> / works fine on windows, and doesn't require escaping ("/foo/bar").
>
> On Fri, Mar 18, 2011 at 2:56 PM, Jon Herman <jfc.herman at gmail.com> wrote:
>
>> Jack,
>>
>> thanks.
>>
>> Alright, so what I did is create a file called hello.txt with a single
>> line of text in there. I then did the following:
>>
>> f="fulldirectory\hello.txt" (where fulldirectory is of course the actual
>> full directory on my computer)
>> open("f", "w")
>>
>> And I get the following error: IOError: [Errno 13] Permission denied: 'f'
>> If I open to read, I get: IOError: [Errno 2] No such file or directory:
>> 'f'
>>
>> Can anyone explain to me why this happens?
>>
>>
>>
>>
>>
>> On Fri, Mar 18, 2011 at 3:50 PM, Jack Trades <jacktradespublic at gmail.com>wrote:
>>
>>>
>>> On Fri, Mar 18, 2011 at 4:33 PM, Jon Herman <jfc.herman at gmail.com>wrote:
>>>
>>>> Hello all,
>>>>
>>>> I am pretty new to Python and am trying to write data to a file.
>>>> However, I seem to be misunderstanding how to do so. For starters, I'm not
>>>> even sure where Python is looking for these files or storing them. The
>>>> directories I have added to my PYTHONPATH variable (where I import modules
>>>> from succesfully) does not appear to be it.
>>>>
>>>> So my question is: How do I tell Python where to look for opening files,
>>>> and where to store new files?
>>>>
>>>> Thanks,
>>>>
>>>> Jon
>>>>
>>>>
>>> By default Python will read and write files from the directory that your
>>> program is run from.  This cannot always be relied upon though (for instance
>>> if your program was imported as a module from another program).
>>>
>>> To find out what directory your program is currently in use os.getcwd().
>>> Here's an example I just ran...
>>>
>>> >>> import os
>>> >>> os.getcwd()
>>> '/media/DATA/code/lispy/liSpy'
>>>
>>> The folder that is returned from os.getcwd() is the folder that "open"
>>> will use.  You can specify another folder by giving the full path.
>>>
>>> open("/full/path/to/file.txt", "w")
>>>
>>> PYTHONPATH is for importing modules, which is a separate concern.
>>>
>>> --
>>> Jack Trades
>>> Pointless Programming Blog <http://pointlessprogramming.wordpress.com>
>>>
>>>
>>
>> --
>>
>> http://mail.python.org/mailman/listinfo/python-list
>>
>>
>
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