YAML
in [Python]
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From: John Bokma on 4 Feb 2010 12:49 Lou Pecora <pecora(a)anvil.nrl.navy.mil> writes: > In article <87eil1ddjp.fsf_-_(a)castleamber.com>, > John Bokma <john(a)castleamber.com> wrote: > >> Lou Pecora <pecora(a)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. My C++ is rusty to say the least, so I can't give you an example in C++, and the C++ version will be longer than the Python version for sure. I use YAML, YAML::Syck to be precise, now and then in Perl. In Perl, if $data is a reference to an arbitrary (complex) datastructure: DumpFile( 'filename', $data ); writes it out and $data = LoadFile( 'filename' ); reads it back in. Since YAML is to some extent human readable, I now and then use it for debugging purposes over Data::Dumper, also because the output is more compact, e.g. die Dump $data; Personally I think it's good to be aware of YAML, since it's supported by several languages and it should in general be possible to exchange the generated YAML between them. -- John Bokma j3b Hacking & Hiking in Mexico - http://johnbokma.com/ http://castleamber.com/ - Perl & Python Development
From: John Bokma on 4 Feb 2010 16:18 Steven D'Aprano <steve(a)REMOVE-THIS-cybersource.com.au> writes: > 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. Regarding malicious data, from the Loading YAML section of PyYAML: Warning: It is not safe to call yaml.load with any data received from an untrusted source! yaml.load is as powerful as pickle.load and so may call any Python function. Check the yaml.safe_load function though. http://pyyaml.org/wiki/PyYAMLDocumentation#LoadingYAML yaml.safe_load however, limits to simple Python objects and Python objects you mark as safe. -- John Bokma j3b Hacking & Hiking in Mexico - http://johnbokma.com/ http://castleamber.com/ - Perl & Python Development
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