[Tutor] beginner question
When writing a simple for loop like so: for x in f where f is the name of a file object, how does Python "know" to interpret the variable x as a line of text, rather than,say, an individual character in the file? Does it automatically treat text files as sequences of lines? -- Mayo Adams 287 Erwin Rd. Chapel Hill, NC 27514 (919)-968-7889 mayoad...@gmail.com ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] Writing processed text to another file(beginner)
Code to build a list z to contain all the first words in each line of a
text file:
z=[]
f=open('C:/atextfile.txt')
for aLine in f:
str=aLine
a=str.split()
z.append(a)
I would like to work further with the list z once the file has been
stripped, and the list is complete but am so clueless about Python and its
curlybracelessness that I don't know when the for loop terminates.
Obviously I don't want to write to the file after every line is read.
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[Tutor] write list of tuples to file (beginner)
I have a list of tuples of the form (string,integer) that I would like to write to a file with a line break between each. Simply writing to a file object thus for item in tuplelist outputfile.write (item) doesn't work, and I suppose I scarcely expect it should, but I am at a loss to find out how to do it. -- Mayo Adams mayoad...@gmail.com ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] pass tuples to user defined function(beginner)
I am trying to pass a set of tuple strings from a file to a function I
have defined. Each tuple is on a separate line, and looks something
like this:
('note',2048)
The function has two parameters , and is defined thus: def
findindex(dval,ticks):
Apparently, I need to cast the second value as an integer in the body
of the function in order to work with it as such, but when I attempt
int(ticks) I get
ValueError: invalid literal for int() with base 10: '2048)'
Upon searching for elucidation of this on the internet I find nothing
but esoterica, at least as far as I am concerned.
Any pointers would make me happy.
--
Mayo Adams
mayoad...@gmail.com
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Re: [Tutor] pass tuples to user defined function(beginner)
Apologies for my numerous offenses to protocol, and gratitude for the suggestions all around.And yet... as to the notion of a tuple existing in some non-Platonic sense, I suspect I will have carry my confusion away in order to dispel it by further reading. "Wrong on both counts?" Hey, you win! I WAS wrong. But if it is not a tuple that is in the file, it would be helpful to know what it is. Presumably, a string representing a tuple. And as to the matter of representation, I cant immediately see how anything in a script is anything other than a representation of some kind, hence the distinction between representamen and object does no work for me. Yes, I should have been clearer as to what I was trying to achieve, but I underestimated the good will of this community(in most cases)and their willingness to help. For which, as I said, much thanks. On Tue, Nov 29, 2011 at 8:02 AM, Steven D'Aprano wrote: > Peter Otten wrote: > >> And here's the lazy-bastard version: > > [...] >> >> ... print ast.literal_eval(line.strip()) > > Nice! > > > -- > Steven > > > > > ___ > Tutor maillist - Tutor@python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > -- Mayo Adams 287 Erwin Rd. Chapel Hill, NC 27514 (919)-968-7889 mayoad...@gmail.com ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] PLEASE HELP
discrete, not discreet. On Fri, Apr 13, 2018 at 11:38 AM, Neil Cerutti wrote: > On 2018-04-13, David Rock wrote: > > > >> On Apr 13, 2018, at 09:24, Neil Cerutti wrote: > >> > >> On 2018-04-12, Scharrer, Brianna wrote: > >>> Applications of basic language syntax > >>> > >>> Date/time string parsing > >>> > >>> Time stamps on data are often recorded in the standard ISO date > >>> and time format as shown below > >>> 1999-02-14T21:02:37 > 9:02pm on February 14, 1999 > >>> > >>> Write code that when given a datetime string and outputs a > >>> human readable version exactly in the format specified below. > >> > >> I disagree that the first version isn't human readable. It is > >> both human readable and stores the date/time in lexicographic > >> order, which is extremly useful for both humans and machines. > > > > Don???t nitpick the definition of ???human readable;??? it > > isn???t relevant to the assignment and just serves to confuse > > the student. Using the phrase ???human readable??? is just a > > poor choice for describing the assignment parameters: changing > > from one format to another (ISO -> ???standard English??? (for > > lack of a better description of the target format). That???s > > the only thing that matters in this context. > > It is relevant to the assignment if the student hadn't noticed > that the date was human readable. I was hoping to correct this > possible misapprehension resulting from the poor assignment > language. > > -- > Neil Cerutti > > ___ > Tutor maillist - Tutor@python.org > To unsubscribe or change subscription options: > https://mail.python.org/mailman/listinfo/tutor > -- Mayo Adams 287 Erwin Rd. Chapel Hill, NC 27514 (919)-780-3917 mayoad...@gmail.com ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
[Tutor] Environment variables and Flask
I have for some time been flummoxed as to the significance of setting environment variables, for example in order to run a Flask application. What are these environment variables, exactly, and why is it necessary to set them? "Googling" here simply leads me into more arcana, and doesn't really help. -- Mayo Adams ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Environment variables and Flask
Many thanks to some very bright and helpful gentlemen.
On Fri, Jun 28, 2019 at 9:24 AM Mats Wichmann wrote:
> On 6/27/19 11:24 PM, Mayo Adams wrote:
> > I have for some time been flummoxed as to the significance of setting
> > environment variables, for example in order to run a Flask application.
> > What are these environment variables, exactly, and why is it necessary to
> > set them? "Googling" here simply leads me into more arcana, and doesn't
> > really help.
>
> As others have noted, it's a way to pass information from one process to
> another at startup time. Since this is a Python list, I thought it
> might be instructive to show how it works. In Python, you access these
> environment variables through a dictionary in the os module, called
> environ, which "survives" across the call-another-process boundary,
> unlike any normal variables you might set in your program. Here's a
> trivial Python app that is able to recognize those environment variables
> that begin with MYENV_. That points up one issue with environment
> variables right away: it's a namespace you share with everybody, and
> there's a chance someone accidentally is using a variable you think is
> important - because it's important to them in their context, not yours.
> So tricks like special naming conventions may be useful.
>
> In this snip, we build a dictionary from os.environ, using only the keys
> that seem to be "for us":
>
>
> === child.py ===
> import os
>
> myenv = { k: v for k, v in os.environ.items() if "MYENV_" in k }
>
> print("child found these settings:", myenv)
> ==
>
> Now write another script which sets a value, then calls the child
> script; then sets a different value, then calls the child script.
>
> === parent.py ===
> import os
> import subprocess
>
> print("Calling with MYENV_foo set")
> os.environ['MYENV_foo'] = "Yes"
> subprocess.run(["python", "child.py"])
>
> print("Calling with MYENV_bar set")
> os.environ['MYENV_bar'] = "1"
> subprocess.run(["python", "child.py"])
> ==
>
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--
Mayo Adams
287 Erwin Rd.
Chapel Hill, NC 27514
(919)-780-3917
mayoad...@gmail.com
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