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Auto merge of #2566 - micbou:python3, r=puremourning

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[READY] Prefer Python 3 over Python 2

When both versions are available, we should use Python 3 over Python 2 for the following reasons:
 - faster startup:

<table>
  <tr>
    <th rowspan="2">Platform</th>
    <th colspan="2">First run (ms)</th>
    <th colspan="2">Subsequent runs (ms)</th>
  </tr>
  <tr>
    <td>Python 2</td>
    <td>Python 3</td>
    <td>Python 2</td>
    <td>Python 3</td>
  </tr>
  <tr>
    <td>Ubuntu 16.04 64-bit</td>
    <td>197</td>
    <td>110</td>
    <td>117</td>
    <td>84</td>
  </tr>
  <tr>
    <td>macOS 10.12</td>
    <td>322</td>
    <td>186</td>
    <td>210</td>
    <td>124</td>
  </tr>
  <tr>
    <td>Windows 10 64-bit</td>
    <td>601</td>
    <td>295</td>
    <td>251</td>
    <td>144</td>
  </tr>
</table>

*Results obtained by running the `prof.py` script from [this branch](https://github.com/micbou/YouCompleteMe/tree/profiling-startup). The difference between first run and subsequent runs is Python bytecode generation (`*.pyc` files).*

These differences are due to `python-future` monkey-patching a lot of stuff on Python 2 but not on Python 3;

 - better Windows support. For instance, [the `tempfile` module returns temporary paths in all lowercase on Python 2](https://bugs.python.org/issue14255) (we use it to create our logfiles). This is fixed on Python 3.
 - [Python 2 support will be dropped in 2020](https://docs.python.org/devguide/index.html#branchstatus).

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This commit is contained in:
Homu 2017-03-07 16:45:57 +09:00
commit cb2f6d7953
1 changed files with 13 additions and 10 deletions
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autoload/youcompleteme.vim
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@ -28,26 +28,29 @@ let s:cursor_moved = 0
let s:previous_allowed_buffer_number = 0
function! s:UsingPython2()
" I'm willing to bet quite a bit that sooner or later, somebody will ask us to
" make it configurable which version of Python we use.
if has('python')
" When both versions are available, we prefer Python 3 over Python 2:
" - faster startup (no monkey-patching from python-future);
" - better Windows support (e.g. temporary paths are not returned in all
" lowercase);
" - Python 2 support will eventually be dropped.
function! s:UsingPython3()
if has('python3')
return 1
endif
return 0
endfunction
let s:using_python2 = s:UsingPython2()
let s:python_until_eof = s:using_python2 ? "python << EOF" : "python3 << EOF"
let s:python_command = s:using_python2 ? "py " : "py3 "
let s:using_python3 = s:UsingPython3()
let s:python_until_eof = s:using_python3 ? "python3 << EOF" : "python << EOF"
let s:python_command = s:using_python3 ? "py3 " : "py "
function! s:Pyeval( eval_string )
if s:using_python2
return pyeval( a:eval_string )
if s:using_python3
return py3eval( a:eval_string )
endif
return py3eval( a:eval_string )
return pyeval( a:eval_string )
endfunction