Re: YAML (was: Python and Ruby)
In article 00f4bb3a$0$15566$c3e8...@news.astraweb.com, Steven D'Aprano st...@remove-this-cybersource.com.au wrote: On Thu, 04 Feb 2010 09:57:59 -0500, Lou Pecora wrote: Well, that looks a bit more complicated than I would like, but maybe it's doing more stuff than I can grok. Here's what I needed and how I did it in Python: [...] # Reading same list in: instr=fp.readline() inlist=eval(instr) x1,y1,astr1,z1= inlist That's what I needed. 3 lines to write or read a inhomogeneous collection of variables. Easy, but also quick and dirty -- good enough for small scripts, but not really good enough for production applications. I can add more variables, shuffle the order, whatever without messing with formatting, etc. This is nice and easy. But there are at least four catches: * you can't safely treat the data file as human-editable (although a sufficiently careful and Python-aware user could edit it) * you can't use any data that isn't a built-in, or that contains something that is not a built-in * there may be reliability issues with floats - you're at the mercy of changes to the underlying repr of float objects, and it almost certainly will blow up in your face if you get an inf or nan (at least prior to Python 2.6) * you're using eval, which is a security risk if you can't trust the source of the data file. However, be aware that neither marshal nor pickle guarantees to be safe against malicious data either. The docs for both warn against using them on untrusted data. YAML or JSON *might* be safer, I haven't looked. I understand where you are coming from: Production Code. I was just making a point about Python and my code is only used by me. I can edit the file for the simple I/O I do. I am not recommending this way for everyone. Just an example. -- -- Lou Pecora -- http://mail.python.org/mailman/listinfo/python-list
Re: YAML (was: Python and Ruby)
On Fri, 05 Feb 2010 09:22:03 -0500, Lou Pecora wrote: [...] That's what I needed. 3 lines to write or read a inhomogeneous collection of variables. Easy, but also quick and dirty -- good enough for small scripts, but not really good enough for production applications. [...] I understand where you are coming from: Production Code. I was just making a point about Python and my code is only used by me. I can edit the file for the simple I/O I do. I am not recommending this way for everyone. Just an example. We're in violent agreement then :) -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: YAML (was: Python and Ruby)
In article 87eil1ddjp.fsf...@castleamber.com, John Bokma j...@castleamber.com wrote: Lou Pecora pec...@anvil.nrl.navy.mil writes: That's a pretty accurate description of how I transitioned to Python from C and Fortran. Not C, but C++ (but there are also C implementations): YAML, see: http://code.google.com/p/yaml-cpp/wiki/HowToParseADocument I use YAML now and then with Perl for both reading/writing data and for debugging purposes (YAML is quite human readable, for programmers at least) Of course there is also YAML support for Python: http://pyyaml.org/. Well, that looks a bit more complicated than I would like, but maybe it's doing more stuff than I can grok. Here's what I needed and how I did it in Python: # Make some variables x=1.234e-8 y=2 astr=An output string...whatever z=4.5+1j*1.3456 # a complex number # Output them to a file already opened as fp outlist=[x, y, astr, z] repvars= repr(outlist)+\n fp.write(repvars) # Reading same list in: instr=fp.readline() inlist=eval(instr) x1,y1,astr1,z1= inlist That's what I needed. 3 lines to write or read a inhomogeneous collection of variables. I can add more variables, shuffle the order, whatever without messing with formatting, etc. That's pretty easy for me and it's easy for anyone to see and understand what's being done. Not trying to start an argument, just showing how the former messasge I was replying to made a good point about Python's way of doing things and the effort to shake off old habits from other languages. -- -- Lou Pecora -- http://mail.python.org/mailman/listinfo/python-list
Re: YAML (was: Python and Ruby)
On Thu, 04 Feb 2010 09:57:59 -0500, Lou Pecora wrote: Well, that looks a bit more complicated than I would like, but maybe it's doing more stuff than I can grok. Here's what I needed and how I did it in Python: [...] # Reading same list in: instr=fp.readline() inlist=eval(instr) x1,y1,astr1,z1= inlist That's what I needed. 3 lines to write or read a inhomogeneous collection of variables. Easy, but also quick and dirty -- good enough for small scripts, but not really good enough for production applications. I can add more variables, shuffle the order, whatever without messing with formatting, etc. This is nice and easy. But there are at least four catches: * you can't safely treat the data file as human-editable (although a sufficiently careful and Python-aware user could edit it) * you can't use any data that isn't a built-in, or that contains something that is not a built-in * there may be reliability issues with floats - you're at the mercy of changes to the underlying repr of float objects, and it almost certainly will blow up in your face if you get an inf or nan (at least prior to Python 2.6) * you're using eval, which is a security risk if you can't trust the source of the data file. However, be aware that neither marshal nor pickle guarantees to be safe against malicious data either. The docs for both warn against using them on untrusted data. YAML or JSON *might* be safer, I haven't looked. That's pretty easy for me and it's easy for anyone to see and understand what's being done. Not trying to start an argument, just showing how the former messasge I was replying to made a good point about Python's way of doing things and the effort to shake off old habits from other languages. These are all good points. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
