Hi Eric,
I played around with some similar ideas a while back - I just blew the dust
off it and published it here: https://github.com/pwaller/pp2g
My approach is a bit different, and works by printing the Python AST in Go.
There is an overlap in our philosophy of 'produce standalone code' and
'help a human do the translation into idiomatic Go'. However, mine was a
Saturday morning project which was never used in anger, so it is naturally
quite incomplete.
Regards,
- Peter
On Sun, 30 Sep 2018 at 11:48, Eric Raymond <e...@thyrsus.com> wrote:
> I have mentioned before on this list that I am engaged in source
> translation of a largeish Python prgram - 14KLOC - to Go. I found the
> automated AST-based translation tools already available unsatisfactory;
> they don't produce a quality of Go code I would consider maintainable. So
> I wrote my own using crude, old-school regexp-bashing.
>
> This turned out to be surprisingly effective. The following is from the
> manual page:
>
> * Opens Python block scopes with { and closes them with }.
>
> * Changes docstrings to comments.
>
> * Changes comments from #-led to //-led
>
> * Translates Python boolean constants True, False to Go true, false
>
> * Translates Python "in range" to Go ":= range", You will need to fix
> up the comma and range clauses by hand.
>
> * Maps Python single-quote literals to Go double-quote literals.
>
> * Translates Python logical connectives and or not to Go && || !.
>
> * Changes Python None to Go nil.
>
> * Changes "def " at the left margin to "func ".
>
> * Common cases of various Python string library methods - capitalize(),
> count(), endswith(), find(), join(), lower(), lstrip(), rfind(), replace(),
> rstrip(), split(), startswith(), split(), upper() - are translated to Go
> string library calls.
>
> * Some common Python standard library calls, notably from os and
> os.filepath, are translated into Go equivalents. The result is not
> guaranteed to be perfectly correct; a Python call that throws a signal on
> failure may map into a Go function with an error return. But it will always
> be a step in the right direction, and the Go compiler will respond with
> indicative error messages.
>
> * The append() method of Python is translated to a call to Go's append
> intrinsic.
>
> * Python's "del foo[bar]" is translated to Go "delete(foo, bar)". Note
> that this can false-match on a list del with a numeric key; this
> will throw a compilation error in Go and you can hand-fix it.
>
> * Trailing line-continuation backslashes are removed.
>
> * Python r-prefix string literals become Go backtick literals
>
> * Python try/finally/catch become pseudo-statements with delimited block
> scopes. You will need to fix these up by hand.
>
> * Single-line % expressions with a string-literal left hand and either
> tuple or single-variable right hands are translated into fmt.Sprintf
> calls. You will need to translate %-cookies by hand; %r -> %v or %q is the
> usual trouble spot.
>
> * Changes multiline strings to backtick literals. You'll need to fix up
> backslash escapes and %-cookies yourself.
>
> * Many, but not necessarily all, cases where Go ":=" assignment can
> replace a plain "=" assignment in Python are translated.
>
> This doesn't do a complete job, of course. But it takes a lot of the pain
> out of hand-translation, and it does preserve comments and structure.
> Probably the automated block scope closing is the biggest single win;
> that's a tedious, fiddly job by hand and mistakes are all too easy.
>
> Future releases will translate a larger subset of Python standard library
> calls.
>
> The repository is at https://gitlab.com/esr/pytogo and the project home
> page at http://www.catb.org/esr/pytogo/
>
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