Search for python3 in unix virtual environments (#3798)

crates/uv-interpreter/src/virtualenv.rs

@@ -115,8 +115,19 @@ pub(crate) fn virtualenv_python_executable(venv: impl AsRef<Path>) -> PathBuf {
         // If none of these exist, return the standard location
         default_executable
     } else {
-        // Search for `python` in the `bin` directory.
+        // Check for both `python3` over `python`, preferring the more specific one
-        venv.join("bin").join("python")
+        let default_executable = venv.join("bin").join("python3");
+        if default_executable.exists() {
+            return default_executable;
+        }
+
+        let executable = venv.join("bin").join("python");
+        if executable.exists() {
+            return executable;
+        }
+
+        // If none of these exist, return the standard location
+        default_executable
     }
 }
 

crates/uv/tests/pip_compile.rs

@@ -152,7 +152,7 @@ fn missing_venv() -> Result<()> {
 
         ----- stderr -----
         warning: Requirements file requirements.in does not contain any dependencies
-        error: failed to canonicalize path `[VENV]/bin/python`
+        error: failed to canonicalize path `[VENV]/bin/python3`
           Caused by: No such file or directory (os error 2)
         "###
         );

crates/uv/tests/pip_sync.rs

@@ -119,7 +119,7 @@ fn missing_venv() -> Result<()> {
         ----- stdout -----
 
         ----- stderr -----
-        error: failed to canonicalize path `[VENV]/bin/python`
+        error: failed to canonicalize path `[VENV]/bin/python3`
           Caused by: No such file or directory (os error 2)
         "###);
     }