[Tutor] Tutor Digest, Vol 132, Issue 51
Tim Johnson
pavementii at gmail.com
Sat Feb 21 17:48:51 CET 2015
Hi Guys,
Very simple question, I imagine.
this code throws of off a "counter not defined error".
Can you help?
*def word_counter(word, string):*
* counter = 0*
* for item in string:*
* if item == word:*
* counter = counter + 1*
*print counter*
Thanks,
Tim
--
Tim Johnson
pavementii at gmail.com
c. (267) 630-0369 (text is okay)
f. (267) 352-6298
On Sat, Feb 21, 2015 at 5:00 AM, <tutor-request at python.org> wrote:
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> Today's Topics:
>
> 1. Re: updating a dictionary (Chris Stinemetz)
> 2. Re: updating a dictionary (Danny Yoo)
> 3. Re: subprocess outputing wrong info to command line
> (Steven D'Aprano)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 20 Feb 2015 17:47:29 -0600
> From: Chris Stinemetz <chrisstinemetz at gmail.com>
> To: Mark Lawrence <breamoreboy at yahoo.co.uk>
> Cc: tutor at python.org
> Subject: Re: [Tutor] updating a dictionary
> Message-ID:
> <
> CA+HbpzjJe-QZTVL0hdRT_UmATam7c8fWSWHkOd6GwEeTvfmahg at mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
>
> On Fri, Feb 20, 2015 at 4:51 PM, Mark Lawrence <breamoreboy at yahoo.co.uk>
> wrote:
>
> > On 20/02/2015 17:56, Chris Stinemetz wrote:
> >
> > Please don't top post as it makes long threads difficult if not
> impossible
> > to follow, thanks.
> >
> > I am getting closer. I think I have figured out the logic. I just have a
> >> quick question. How do you access key:values in a nested dictionary?
> >>
> >> MOL02997_C': [{'2': '0', '7': '0', '8': '0', '9': '0'}]}
> >>
> >
> >
> >> say I want to access the key:value 8:0
> >>
> >> print dict['MOL02997_C']['8'] doesn't seem to work.
> >>
> >
> > "doesn't seem to work" doesn't tell us much, so normally you would post
> > your code and the full traceback that you get. However what you have
> seems
> > to be a dictionary that you've called dict, hence overriding the Python
> > built-in name. This isn't illegal but it's certainly frowned upon. For
> > the key 'MOL02997_C' you have a list which holds one dict which contains
> a
> > value '8' amongst others. Hence:-
> >
> > >>> mystruct = {'MOL02997_C': [{'2': '0', '7': '0', '8': '0', '9': '0'}]}
> > >>> mystruct
> > {'MOL02997_C': [{'7': '0', '8': '0', '2': '0', '9': '0'}]}
> > >>> mystruct['MOL02997_C']
> > [{'7': '0', '8': '0', '2': '0', '9': '0'}]
> > >>> mystruct['MOL02997_C'][0]
> > {'7': '0', '8': '0', '2': '0', '9': '0'}
> > >>> mystruct['MOL02997_C'][0]['8']
> > '0'
> >
> > Got that?
> >
> >
> >
> ?
> Thank you Mark.
>
> I understand what you are explaining to me but I am not sure why every
> instance of the key 8:value changes when I assign a new value to it.
>
> I am expecting only vals['KSL04523_A'][0]['8'] value to change to 55.55 but
> as you can see bellow all rows in the dictionary are changes for key 8:
>
> Thank you in advance
>
> >>> vals['KSL04523_A']
> [{'7': '0', '9': '0', '8': '0', '2': '0'}]
> >>> vals['KSL04523_A'][0]
> {'7': '0', '9': '0', '8': '0', '2': '0'}
>
>
> >>> vals['KSL04523_A'][0]['8']
> '0'
>
>
> >>> vals['KSL04523_A'][0]['8'] = 55.55
> >>> pprint.pprint(vals)
> {'CELL_': [{'2': '0', '7': '0', '8': 55.55, '9': '0'}],
> 'KSL04514_B': [{'2': '0', '7': '0', '8': 55.55, '9': '0'}],
> 'KSL04514_C': [{'2': '0', '7': '0', '8': 55.55, '9': '0'}],
> 'KSL04515_A': [{'2': '0', '7': '0', '8': 55.55, '9': '0'}],
> 'KSL04515_B': [{'2': '0', '7': '0', '8': 55.55, '9': '0'}],
> 'KSL04515_C': [{'2': '0', '7': '0', '8': 55.55, '9': '0'}],
> 'KSL04516_A': [{'2': '0', '7': '0', '8': 55.55, '9': '0'}],
> 'KSL04516_B': [{'2': '0', '7': '0', '8': 55.55, '9': '0'}],
> 'KSL04516_C': [{'2': '0', '7': '0', '8': 55.55, '9': '0'}],
> 'KSL04517_A': [{'2': '0', '7': '0', '8': 55.55, '9': '0'}],
> 'KSL04517_B': [{'2': '0', '7': '0', '8': 55.55, '9': '0'}],
> 'KSL04517_C': [{'2': '0', '7': '0', '8': 55.55, '9': '0'}],
> 'KSL04519_A': [{'2': '0', '7': '0', '8': 55.55, '9': '0'}],
> 'KSL04519_B': [{'2': '0', '7': '0', '8': 55.55, '9': '0'}],
> 'KSL04519_C': [{'2': '0', '7': '0', '8': 55.55, '9': '0'}],
> 'KSL04520_A': [{'2': '0', '7': '0', '8': 55.55, '9': '0'}],
> 'KSL04520_B': [{'2': '0', '7': '0', '8': 55.55, '9': '0'}],
> 'KSL04520_C': [{'2': '0', '7': '0', '8': 55.55, '9': '0'}],
> 'KSL04521_A': [{'2': '0', '7': '0', '8': 55.55, '9': '0'}],
> 'KSL04521_B': [{'2': '0', '7': '0', '8': 55.55, '9': '0'}],
> 'KSL04521_C': [{'2': '0', '7': '0', '8': 55.55, '9': '0'}],
> 'KSL04523_A': [{'2': '0', '7': '0', '8': 55.55, '9': '0'}]}?
>
>
> ------------------------------
>
> Message: 2
> Date: Fri, 20 Feb 2015 17:43:23 -0800
> From: Danny Yoo <dyoo at hashcollision.org>
> To: Chris Stinemetz <chrisstinemetz at gmail.com>
> Cc: Mark Lawrence <breamoreboy at yahoo.co.uk>, Python Tutor Mailing List
> <tutor at python.org>
> Subject: Re: [Tutor] updating a dictionary
> Message-ID:
> <CAGZAPF5dddoc6cxegF=
> egnYR4KTqMWg-xfWW0rMSEEZppBdnww at mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
>
> On Fri, Feb 20, 2015 at 3:47 PM, Chris Stinemetz
> <chrisstinemetz at gmail.com> wrote:
> >
> > I understand what you are explaining to me but I am not sure why every
> > instance of the key 8:value changes when I assign a new value to it.
>
>
> Ah. Be wary of structure sharing when the values being shared are mutable.
>
>
> A textbook example of this would be:
>
> ###########################################
> message = ['hello', 'world']
> copy = message
> copy.append('!')
> print copy
> print message
> ## What do we expect to see here? What do we see?
> ###########################################
>
> The code above here is wrong to use the word "copy" here, because it's
> not copying the structure at all. copy refers to the *same* list
> value. Mutations to the value will be observable when we access that
> list through either 'message' or 'copy', since fundamentally they're
> both referring to the same list value.
>
> To copy a list, we can use a whole slice:
>
> #####################
> message = ['hello', 'world']
> copy = message[:]
> copy.append('!')
> print copy
> print message
> #####################
>
>
> I don't know what your program looks like at this point, so I can't
> pinpoint exactly where this is happening, but at the very least, this
> should help you figure out what's going on.
>
> Feel free to ask if you'd like more explanation. If you'd like a
> visualization, also see:
>
> http://pythontutor.com/visualize.html#code=message+%3D+%5B'hello
> ',+'world'%5D%0Acopy+%3D+message%0Acopy.append('!')&mode=display&origin=opt-frontend.js&cumulative=false&heapPrimitives=false&textReferences=false&py=2&rawInputLstJSON=%5B%5D&curInstr=0
>
> and compare vs:
>
> http://pythontutor.com/visualize.html#code=message+%3D+%5B'hello
> ',+'world'%5D%0Acopy+%3D+message%5B%3A%5D%0Acopy.append('!')&mode=display&origin=opt-frontend.js&cumulative=false&heapPrimitives=false&textReferences=false&py=2&rawInputLstJSON=%5B%5D&curInstr=0
>
>
> Good luck!
>
>
> ------------------------------
>
> Message: 3
> Date: Sat, 21 Feb 2015 13:58:20 +1100
> From: Steven D'Aprano <steve at pearwood.info>
> To: tutor at python.org
> Subject: Re: [Tutor] subprocess outputing wrong info to command line
> Message-ID: <20150221025815.GG7655 at ando.pearwood.info>
> Content-Type: text/plain; charset=us-ascii
>
> On Fri, Feb 20, 2015 at 06:58:17PM -0500, brads wrote:
>
> > My subprocess is in error but the same command at the command line works
> > fine.
>
> Are you running the Python script as the same user and from the same
> location as the command line? If you are running the Python script as an
> unprivileged user from your home directory, and the command line as root
> from the directory holding the key, then it is not surprising that they
> will get different results.
>
> Does the dnssec-signzone command use any environment variables? Perhaps
> they are not being inherited by the Python subprocess.
>
> Also, a note about sending code to the list. For some reason, every line
> in your code is separated by blank lines:
>
> > # cat makekeys.py
> >
> > #!/usr/bin/python3.4
> >
> > import subprocess
> >
> > import sys
>
> etc. That makes it very hard to read. Please fix that.
>
> Secondly, you have a huge amount of extraneous code which is irrelevant
> to your problem with subprocess. You calculate dates, ask the user for
> input, delete files, and write new files, calculate arrays and more.
> None of that has anything to do with subprocess. Take it out. Reduce
> your problem to the smallest possible code which shows the problem. 9
> times out of 10, the process of cutting your code down to manageable
> size will actually help you to solve your own problem, and the other 1
> time out of 10 we have a smaller and less confusing piece of code to try
> to understand.
>
> You also have dead, obsolete code commented out. Comments should not be
> used for keeping history in the file, comments should be used for
> commenting about the code. Best practice is to use a revision control
> system like hg, but if you're not up to that at least delete the dead
> code before posting.
>
> When running into a problem with subprocess, your first step should be
> to *exactly* duplicate the successful command:
>
> dnssec-signzone -e20180330000000 -p -t -g -k Ktest123.com.ksk.key -o
> test123.com test123.com.external Ktest123.com.zsk.key
>
>
> So you should try running that from subprocess:
>
> subprocess.call([
> 'dnssec-signzone', '-e20180330000000', '-p', '-t', '-g',
> '-k', 'Ktest123.com.ksk.key', '-o', 'test123.com',
> 'test123.com.external', 'Ktest123.com.zsk.key',
> ])
>
>
> and see if it still works. If it still does not work, that strongly
> suggests a problem with the environment: you are running it as the wrong
> user, in the wrong location, missing enviromnent variables or
> permissions. If it works in Python, then you can start replacing each
> constant argument with a calculated argument, *one argument at a time*,
> and see where you introduce the bug.
>
>
>
> --
> Steve
>
>
> ------------------------------
>
> Subject: Digest Footer
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> ------------------------------
>
> End of Tutor Digest, Vol 132, Issue 51
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