WIP: Use assign expr for "while True: ... break"

Lib/_pydecimal.py

@@ -2778,12 +2778,8 @@ def sqrt(self, context=None):
 
         # find n = floor(sqrt(c)) using Newton's method
         n = 10**prec
-        while True:
-            q = c//n
-            if n <= q:
-                break
-            else:
-                n = n + q >> 1
+        while (q := c//n) < n:
+            n = n + q >> 1
         exact = exact and n*n == c
 
         if exact:

Lib/_pyio.py

@@ -588,10 +588,7 @@ def read(self, size=-1):
     def readall(self):
         """Read until EOF, using multiple read() call."""
         res = bytearray()
-        while True:
-            data = self.read(DEFAULT_BUFFER_SIZE)
-            if not data:
-                break
+        while (data := self.read(DEFAULT_BUFFER_SIZE)):
             res += data
         if res:
             return bytes(res)

Lib/aifc.py

@@ -943,9 +943,6 @@ def openfp(f, mode=None):
             print("Writing", gn)
             with open(gn, 'w') as g:
                 g.setparams(f.getparams())
-                while 1:
-                    data = f.readframes(1024)
-                    if not data:
-                        break
+                while (data := f.readframes(1024)):
                     g.writeframes(data)
             print("Done.")

Lib/asyncio/sslproto.py

@@ -196,11 +196,8 @@ def feed_ssldata(self, data, only_handshake=False):
 
             if self._state == _WRAPPED:
                 # Main state: read data from SSL until close_notify
-                while True:
-                    chunk = self._sslobj.read(self.max_size)
+                while (chunk := self._sslobj.read(self.max_size)):
                     appdata.append(chunk)
-                    if not chunk:  # close_notify
-                        break
 
             elif self._state == _SHUTDOWN:
                 # Call shutdown() until it doesn't raise anymore.

Lib/asyncio/streams.py

@@ -629,10 +629,7 @@ async def read(self, n=-1):
             # deadlock if the subprocess sends more than self.limit
             # bytes.  So just call self.read(self._limit) until EOF.
             blocks = []
-            while True:
-                block = await self.read(self._limit)
-                if not block:
-                    break
+            while (block := await self.read(self._limit)):
                 blocks.append(block)
             return b''.join(blocks)
 

Lib/asyncio/windows_events.py

@@ -699,10 +699,7 @@ def _poll(self, timeout=None):
             if ms >= INFINITE:
                 raise ValueError("timeout too big")
 
-        while True:
-            status = _overlapped.GetQueuedCompletionStatus(self._iocp, ms)
-            if status is None:
-                break
+        while (status := _overlapped.GetQueuedCompletionStatus(self._iocp, ms)) is not None:
             ms = 0
 
             err, transferred, key, address = status

Lib/base64.py

@@ -490,25 +490,16 @@ def b85decode(b):
 
 def encode(input, output):
     """Encode a file; input and output are binary files."""
-    while True:
-        s = input.read(MAXBINSIZE)
-        if not s:
-            break
-        while len(s) < MAXBINSIZE:
-            ns = input.read(MAXBINSIZE-len(s))
-            if not ns:
-                break
+    while (s := input.read(MAXBINSIZE)):
+        while len(s) < MAXBINSIZE and (ns := input.read(MAXBINSIZE-len(s))):
             s += ns
         line = binascii.b2a_base64(s)
         output.write(line)
 
 
 def decode(input, output):
     """Decode a file; input and output are binary files."""
-    while True:
-        line = input.readline()
-        if not line:
-            break
+    while (line := input.readline()):
         s = binascii.a2b_base64(line)
         output.write(s)
 

Lib/binhex.py

@@ -237,16 +237,12 @@ def binhex(inp, out):
 
     with io.open(inp, 'rb') as ifp:
         # XXXX Do textfile translation on non-mac systems
-        while True:
-            d = ifp.read(128000)
-            if not d: break
+        while (d := ifp.read(128000)):
             ofp.write(d)
         ofp.close_data()
 
     ifp = openrsrc(inp, 'rb')
-    while True:
-        d = ifp.read(128000)
-        if not d: break
+    while (d := ifp.read(128000)):
         ofp.write_rsrc(d)
     ofp.close()
     ifp.close()
@@ -460,19 +456,15 @@ def hexbin(inp, out):
 
     with io.open(out, 'wb') as ofp:
         # XXXX Do translation on non-mac systems
-        while True:
-            d = ifp.read(128000)
-            if not d: break
+        while (d := ifp.read(128000)):
             ofp.write(d)
     ifp.close_data()
 
     d = ifp.read_rsrc(128000)
     if d:
         ofp = openrsrc(out, 'wb')
         ofp.write(d)
-        while True:
-            d = ifp.read_rsrc(128000)
-            if not d: break
+        while (d := ifp.read_rsrc(128000)):
             ofp.write(d)
         ofp.close()
 

Lib/chunk.py

@@ -31,10 +31,7 @@
     except EOFError:
         break
     chunktype = chunk.getname()
-    while True:
-        data = chunk.read(nbytes)
-        if not data:
-            pass
+    while (data := chunk.read(nbytes)):
         # do something with data
 
 The interface is file-like.  The implemented methods are:

Lib/fnmatch.py

@@ -103,10 +103,7 @@ def translate(pat):
                 else:
                     chunks = []
                     k = i+2 if pat[i] == '!' else i+1
-                    while True:
-                        k = pat.find('-', k, j)
-                        if k < 0:
-                            break
+                    while (k := pat.find('-', k, j)) >= 0:
                         chunks.append(pat[i:k])
                         i = k+1
                         k = k+3

Lib/ftplib.py

@@ -440,10 +440,7 @@ def retrbinary(self, cmd, callback, blocksize=8192, rest=None):
         """
         self.voidcmd('TYPE I')
         with self.transfercmd(cmd, rest) as conn:
-            while 1:
-                data = conn.recv(blocksize)
-                if not data:
-                    break
+            while (data := conn.recv(blocksize)):
                 callback(data)
             # shutdown ssl layer
             if _SSLSocket is not None and isinstance(conn, _SSLSocket):
@@ -502,10 +499,7 @@ def storbinary(self, cmd, fp, blocksize=8192, callback=None, rest=None):
         """
         self.voidcmd('TYPE I')
         with self.transfercmd(cmd, rest) as conn:
-            while 1:
-                buf = fp.read(blocksize)
-                if not buf:
-                    break
+            while (buf := fp.read(blocksize)):
                 conn.sendall(buf)
                 if callback:
                     callback(buf)

Lib/getpass.py

@@ -102,10 +102,7 @@ def win_getpass(prompt='Password: ', stream=None):
     for c in prompt:
         msvcrt.putwch(c)
     pw = ""
-    while 1:
-        c = msvcrt.getwch()
-        if c == '\r' or c == '\n':
-            break
+    while (c := msvcrt.getwch()) not in ('\r', '\n'):
         if c == '\003':
             raise KeyboardInterrupt
         if c == '\b':

Lib/gzip.py

@@ -560,10 +560,7 @@ def _test():
             else:
                 f = builtins.open(arg, "rb")
                 g = open(arg + ".gz", "wb")
-        while True:
-            chunk = f.read(1024)
-            if not chunk:
-                break
+        while (chunk := f.read(1024)):
             g.write(chunk)
         if g is not sys.stdout.buffer:
             g.close()

Lib/mailbox.py

@@ -679,11 +679,8 @@ def flush(self):
                 self._file.seek(start)
                 self._pre_message_hook(new_file)
                 new_start = new_file.tell()
-                while True:
-                    buffer = self._file.read(min(4096,
-                                                 stop - self._file.tell()))
-                    if not buffer:
-                        break
+                while (buffer := self._file.read(min(4096,
+                                                     stop - self._file.tell()))):
                     new_file.write(buffer)
                 new_toc[key] = (new_start, new_file.tell())
                 self._post_message_hook(new_file)
@@ -1422,10 +1419,8 @@ def _install_message(self, message):
                     self._file.write(line.replace(b'\n', linesep))
                     if line == b'\n' or not line:
                         break
-            while True:
-                buffer = orig_buffer.read(4096) # Buffer size is arbitrary.
-                if not buffer:
-                    break
+            # Buffer size is arbitrary.
+            while (buffer := orig_buffer.read(4096)):
                 self._file.write(buffer.replace(b'\n', linesep))
         elif isinstance(message, (bytes, str, io.StringIO)):
             if isinstance(message, io.StringIO):
@@ -1465,10 +1460,7 @@ def _install_message(self, message):
                         message.seek(original_pos)
                     else:
                         break
-            while True:
-                line = message.readline()
-                if not line:
-                    break
+            while (line := message.readline()):
                 # Universal newline support.
                 if line.endswith(b'\r\n'):
                     line = line[:-2] + linesep
@@ -1953,10 +1945,7 @@ def readlines(self, sizehint=None):
 
     def __iter__(self):
         """Iterate over lines."""
-        while True:
-            line = self.readline()
-            if not line:
-                return
+        while (line := self.readline()):
             yield line
 
     def tell(self):

Lib/mailcap.py

@@ -78,9 +78,7 @@ def _readmailcapfile(fp, lineno):
     the viewing command is stored with the key "view".
     """
     caps = {}
-    while 1:
-        line = fp.readline()
-        if not line: break
+    while (line := fp.readline()):
         # Ignore comments and blank lines
         if line[0] == '#' or line.strip() == '':
             continue

Lib/mimetypes.py

@@ -212,10 +212,7 @@ def readfp(self, fp, strict=True):
         list of standard types, else to the list of non-standard
         types.
         """
-        while 1:
-            line = fp.readline()
-            if not line:
-                break
+        while (line := fp.readline()):
             words = line.split()
             for i in range(len(words)):
                 if words[i][0] == '#':

Lib/nntplib.py

@@ -481,19 +481,13 @@ def _getlongresp(self, file=None):
             if file is not None:
                 # XXX lines = None instead?
                 terminators = (b'.' + _CRLF, b'.\n')
-                while 1:
-                    line = self._getline(False)
-                    if line in terminators:
-                        break
+                while (line := self._getline(False)) not in terminators:
                     if line.startswith(b'..'):
                         line = line[1:]
                     file.write(line)
             else:
                 terminator = b'.'
-                while 1:
-                    line = self._getline()
-                    if line == terminator:
-                        break
+                while (line := self._getline()) != terminator:
                     if line.startswith(b'..'):
                         line = line[1:]
                     lines.append(line)

Lib/platform.py

@@ -572,10 +572,7 @@ def _platform(*args):
     platform = platform.replace('unknown', '')
 
     # Fold '--'s and remove trailing '-'
-    while 1:
-        cleaned = platform.replace('--', '-')
-        if cleaned == platform:
-            break
+    while (cleaned := platform.replace('--', '-')) != platform:
         platform = cleaned
     while platform[-1] == '-':
         platform = platform[:-1]

Lib/posixpath.py

@@ -301,10 +301,7 @@ def expandvars(path):
         end = '}'
         environ = os.environ
     i = 0
-    while True:
-        m = search(path, i)
-        if not m:
-            break
+    while (m := search(path, i)):
         i, j = m.span(0)
         name = m.group(1)
         if name.startswith(start) and name.endswith(end):

Lib/py_compile.py

@@ -178,10 +178,7 @@ def main(args=None):
         args = sys.argv[1:]
     rv = 0
     if args == ['-']:
-        while True:
-            filename = sys.stdin.readline()
-            if not filename:
-                break
+        while (filename := sys.stdin.readline()):
             filename = filename.rstrip('\n')
             try:
                 compile(filename, doraise=True)

Lib/pydoc.py

@@ -595,9 +595,7 @@ def markup(self, text, escape=None, funcs={}, classes={}, methods={}):
                                 r'RFC[- ]?(\d+)|'
                                 r'PEP[- ]?(\d+)|'
                                 r'(self\.)?(\w+))')
-        while True:
-            match = pattern.search(text, here)
-            if not match: break
+        while (match := pattern.search(text, here)):
             start, end = match.span()
             results.append(escape(text[here:start]))
 

Lib/quopri.py

@@ -67,10 +67,7 @@ def write(s, output=output, lineEnd=b'\n'):
             output.write(s + lineEnd)
 
     prevline = None
-    while 1:
-        line = input.readline()
-        if not line:
-            break
+    while (line := input.readline()):
         outline = []
         # Strip off any readline induced trailing newline
         stripped = b''
@@ -126,9 +123,7 @@ def decode(input, output, header=False):
         return
 
     new = b''
-    while 1:
-        line = input.readline()
-        if not line: break
+    while (line := input.readline()):
         i, n = 0, len(line)
         if n > 0 and line[n-1:n] == b'\n':
             partial = 0; n = n-1

Lib/re.py

@@ -349,13 +349,7 @@ def scan(self, string):
         append = result.append
         match = self.scanner.scanner(string).match
         i = 0
-        while True:
-            m = match()
-            if not m:
-                break
-            j = m.end()
-            if i == j:
-                break
+        while (m := match()) and (j := m.end()) == i:
             action = self.lexicon[m.lastindex-1][1]
             if callable(action):
                 self.match = m