Merge pull request #1548 from rstudio/dont-discover-python2

don't discover python2 in `py_discover_config()`

NEWS.md

@@ -1,19 +1,22 @@
 # reticulate (development version)
 
-- `iterate(simplify=TRUE)` rewritten in C for speed improvements. 
+- `iterate(simplify=TRUE)` rewritten in C for speed improvements.
 
-- Fixed hang encountered (sometimes) when attempting to call `iterate()` 
+- Fixed hang encountered (sometimes) when attempting to call `iterate()`
   on an exhausted `py_iterator()` object multiple times.
 
 - Update for Pandas 2.2 deprecation of `Index.format()` (#1537, #1538).
 
 - Updates for CRAN R-devel (R 4.4).
 
+- Fixed an issue where `py_discover_config()` would discover `python` (v2) on the PATH
+  in preference of `python3` on the PATH. (#1547)
+
 # reticulate 1.35.0
 
 - Subclassed Python list and dict objects are no longer automatically converted
   to R vectors. Additionally, the S3 R `class` attribute for Python objects is
-  now constructed using the Python `type(object)` directly, rather than from the 
+  now constructed using the Python `type(object)` directly, rather than from the
   `object.__class__` attribute. See #1531 for details and context.
 
 - R external pointers (EXTPTRSXP objects) now round-trip through
@@ -29,7 +32,7 @@
 - Added support for partially unexpanded variables like `$USER` in
   `XDG_DATA_HOME` and similar (#1513, #1514)
 
-## Knitr Python Engine Changes: 
+## Knitr Python Engine Changes:
 
 - The knitr python engine now formats captured python exceptions to include the
   exception type and any exception notes when chunk options
@@ -46,7 +49,7 @@
   where matplotlib was first imported would be the wrong size
   (reported in #1523, fixed in #1530)
 
-- Fixed an issue where the knitr engine would not correctly display altair 
+- Fixed an issue where the knitr engine would not correctly display altair
   compound charts if more than one were present in a document (#1500, #1532).
 
 # reticulate 1.34.0
@@ -160,7 +163,7 @@
 - The knitr engine gains a `jupyter_compat` option, enabling
   reticulate to better match the behavior of Jupyter. When this chunk
   option is set to `TRUE`, only the return value from the last
-  expression in a chunk is auto-printed. 
+  expression in a chunk is auto-printed.
   (#1391, #1394, contributed by @matthew-brett)
 
 - The knitr engine now more reliably detects and displays matplotlib

R/config.R

@@ -306,6 +306,7 @@ py_discover_config <- function(required_module = NULL, use_environment = NULL) {
   ## In other words,
   ##  - no use_python(), use_virtualenv(), use_condaenv()
   ##  - no RETICULATE_PYTHON, RETICULATE_PYTHON_ENV, or RETICULATE_PYTHON_FALLBACK env vars
+  ##  - no existing venv in the current working directory named: venv .venv virtualenv or .virtualenv
   ##  - no env named 'r-bar' if there was a call like `import('foo', delay_load = list(environment = "r-bar"))`
   ##  - no env named 'r-foo' if there was a call like `import('foo')`
   ##  - we're not running under an already activated venv (i.e., no VIRTUAL_ENV env var)
@@ -385,13 +386,13 @@ py_discover_config <- function(required_module = NULL, use_environment = NULL) {
 
     # if we have a required module ensure it's satisfied.
     # also check architecture (can be an issue on windows)
-    has_python_gte_27 <- as.numeric_version(config$version) >= "2.7"
+    has_python_gte_36 <- as.numeric_version(config$version) >= "3.6"
     has_compatible_arch <- !is_incompatible_arch(config)
     has_preferred_numpy <- !is.null(config$numpy) && config$numpy$version >= "1.6"
     if (has_compatible_arch && has_preferred_numpy)
-      valid_python_versions <- c(valid_python_versions, python_version)
+      append(valid_python_versions) <- python_version
     has_required_module <- is.null(config$required_module) || !is.null(config$required_module_path)
-    if (has_python_gte_27 && has_compatible_arch && has_preferred_numpy && has_required_module)
+    if (has_python_gte_36 && has_compatible_arch && has_preferred_numpy && has_required_module)
       return(config)
   }