compile re expressions only if required

python · JelleZijlstra · Apr 30, 2023 · Apr 21, 2023 · Apr 28, 2023 · Apr 28, 2023
commit c8f51fd8df42a4ad2b81fdc3144d5fa8c3f50bfa
diff --git a/Lib/platform.py b/Lib/platform.py
@@ -152,11 +152,6 @@ def _comparable_version(version):

 ### Platform specific APIs

-_libc_search = re.compile(b'(__libc_init)'
-                          b'|'
-                          b'(GLIBC_([0-9.]+))'
-                          b'|'
-                          br'(libc(_\w+)?\.so(?:\.(\d[0-9.]*))?)', re.ASCII)

 def libc_ver(executable=None, lib='', version='', chunksize=16384):

@@ -190,6 +185,12 @@ def libc_ver(executable=None, lib='', version='', chunksize=16384):
            # sys.executable is not set.
            return lib, version

+    _libc_search = re.compile(b'(__libc_init)'
+                          b'|'
+                          b'(GLIBC_([0-9.]+))'
+                          b'|'
+                          br'(libc(_\w+)?\.so(?:\.(\d[0-9.]*))?)', re.ASCII)
+
    V = _comparable_version
    # We use os.path.realpath()
    # here to work around problems with Cygwin not being
@@ -247,9 +248,6 @@ def _norm_version(version, build=''):
    version = '.'.join(strings[:3])
    return version

-_ver_output = re.compile(r'(?:([\w ]+) ([\w.]+) '
-                         r'.*'
-                         r'\[.* ([\d.]+)\])')

 # Examples of VER command output:
 #
@@ -295,6 +293,10 @@ def _syscmd_ver(system='', release='', version='',
    else:
        return system, release, version

+    _ver_output = re.compile(r'(?:([\w ]+) ([\w.]+) '
+                         r'.*'
+                         r'\[.* ([\d.]+)\])')
+
    # Parse the output
    info = info.strip()
    m = _ver_output.match(info)
@@ -1033,18 +1035,6 @@ def processor():

 ### Various APIs for extracting information from sys.version

-_sys_version_parser = re.compile(
-    r'([\w.+]+)\s*'  # "version<space>"
-    r'\(#?([^,]+)'  # "(#buildno"
-    r'(?:,\s*([\w ]*)'  # ", builddate"
-    r'(?:,\s*([\w :]*))?)?\)\s*'  # ", buildtime)<space>"
-    r'\[([^\]]+)\]?', re.ASCII)  # "[compiler]"
-
-_pypy_sys_version_parser = re.compile(
-    r'([\w.+]+)\s*'
-    r'\(#?([^,]+),\s*([\w ]+),\s*([\w :]+)\)\s*'
-    r'\[PyPy [^\]]+\]?')
-
 _sys_version_cache = {}

 def _sys_version(sys_version=None):
@@ -1076,6 +1066,13 @@ def _sys_version(sys_version=None):
    if result is not None:
        return result

+    _sys_version_parser = re.compile(
+        r'([\w.+]+)\s*'  # "version<space>"
+        r'\(#?([^,]+)'  # "(#buildno"
+        r'(?:,\s*([\w ]*)'  # ", builddate"
+        r'(?:,\s*([\w :]*))?)?\)\s*'  # ", buildtime)<space>"
+        r'\[([^\]]+)\]?', re.ASCII)  # "[compiler]"
+
    if sys.platform.startswith('java'):
        # Jython
        name = 'Jython'
@@ -1091,6 +1088,11 @@ def _sys_version(sys_version=None):

    elif "PyPy" in sys_version:
        # PyPy
+        _pypy_sys_version_parser = re.compile(
+            r'([\w.+]+)\s*'
+            r'\(#?([^,]+),\s*([\w ]+),\s*([\w :]+)\)\s*'
+            r'\[PyPy [^\]]+\]?')
+
        name = "PyPy"
        match = _pypy_sys_version_parser.match(sys_version)
        if match is None:
@@ -1290,17 +1292,6 @@ def platform(aliased=False, terse=False):
 ### freedesktop.org os-release standard
 # https://www.freedesktop.org/software/systemd/man/os-release.html

-# NAME=value with optional quotes (' or "). The regular expression is less
-# strict than shell lexer, but that's ok.
-_os_release_line = re.compile(
-    "^(?P<name>[a-zA-Z0-9_]+)=(?P<quote>[\"\']?)(?P<value>.*)(?P=quote)$"
-)
-# unescape five special characters mentioned in the standard
-_os_release_unescape = re.compile(r"\\([\\\$\"\'`])")
-# /etc takes precedence over /usr/lib
-_os_release_candidates = ("/etc/os-release", "/usr/lib/os-release")
-_os_release_cache = None
-

 def _parse_os_release(lines):
    # These fields are mandatory fields with well-known defaults
@@ -1311,6 +1302,14 @@ def _parse_os_release(lines):
        "PRETTY_NAME": "Linux",
    }

+    # NAME=value with optional quotes (' or "). The regular expression is less
+    # strict than shell lexer, but that's ok.
+    _os_release_line = re.compile(
+        "^(?P<name>[a-zA-Z0-9_]+)=(?P<quote>[\"\']?)(?P<value>.*)(?P=quote)$"
+    )
+    # unescape five special characters mentioned in the standard
+    _os_release_unescape = re.compile(r"\\([\\\$\"\'`])")
+
    for line in lines:
        mo = _os_release_line.match(line)
        if mo is not None:
@@ -1326,6 +1325,10 @@ def freedesktop_os_release():
    """
    global _os_release_cache

+    # /etc takes precedence over /usr/lib
+    _os_release_candidates = ("/etc/os-release", "/usr/lib/os-release")
+    _os_release_cache = None
+
    if _os_release_cache is None:
        errno = None
        for candidate in _os_release_candidates: