gh-129011: Update comments in FileIO to match current code (#129012)

1 files changed, 14 insertions, 3 deletions

diff --git a/Lib/_pyio.py b/Lib/_pyio.py
index e915e5b..99d6f79 100644
--- a/Lib/_pyio.py
+++ b/Lib/_pyio.py
@@ -1645,7 +1645,13 @@ class FileIO(RawIOBase):
     def read(self, size=None):
         """Read at most size bytes, returned as bytes.
 
-        Only makes one system call, so less data may be returned than requested
+        If size is less than 0, read all bytes in the file making
+        multiple read calls. See ``FileIO.readall``.
+
+        Attempts to make only one system call, retrying only per
+        PEP 475 (EINTR). This means less data may be returned than
+        requested.
+
         In non-blocking mode, returns None if no data is available.
         Return an empty bytes object at EOF.
         """
@@ -1661,8 +1667,13 @@ class FileIO(RawIOBase):
     def readall(self):
         """Read all data from the file, returned as bytes.
 
-        In non-blocking mode, returns as much as is immediately available,
-        or None if no data is available.  Return an empty bytes object at EOF.
+        Reads until either there is an error or read() returns size 0
+        (indicates EOF). If the file is already at EOF, returns an
+        empty bytes object.
+
+        In non-blocking mode, returns as much data as could be read
+        before EAGAIN. If no data is available (EAGAIN is returned
+        before bytes are read) returns None.
         """
         self._checkClosed()
         self._checkReadable()