Unravelling Python's syntactic sugar source code.
There are accompanying blog posts to go with all of the code in this repository.
-
obj.attr
➠builtins.getattr(obj, "attr")
(includingobject.__getattribute__()
) -
a + b
➠operator.__add__(a, b)
-
a - b
➠operator.__sub__(a, b)
-
a * b
➠operator.__mul__(a, b)
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a @ b
➠operator.__matmul__(a, b)
-
a / b
➠operator.__truediv__(a, b)
-
a // b
➠operator.__floordiv__(a, b)
-
a % b
➠operator.__mod__(a, b)
-
a ** b
➠operator.__pow__(a, b)
-
a << b
➠operator.__lshift__(a, b)
-
a >> b
➠operator.__rshift__(a, b)
-
a & b
➠operator.__and__(a, b)
-
a ^ b
➠operator.__xor__(a, b)
-
a | b
➠operator.__or__(a, b)
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a += b
➠a = operator.__iadd__(a, b)
-
a -= b
➠a = operator.__isub__(a, b)
-
a *= b
➠a = operator.__imul__(a, b)
-
a @= b
➠a = operator.__imatmul__(a, b)
-
a /= b
➠a = operator.__itruediv__(a, b)
-
a //= b
➠a = operator.__ifloordiv__(a, b)
-
a %= b
➠a = operator.__imod__(a, b)
-
a **= b
➠a = operator.__ipow__(a, b)
-
a <<= b
➠a = operator.__ilshift__(a, b)
-
a >>= b
➠a = operator.__irshift__(a, b)
-
a &= b
➠a = operator.__iand__(a, b)
-
a ^= b
➠a = operator.__ixor__(a, b)
-
a |= b
➠a = operator.__ior__(a, b)
-
~ a
➠operator.__invert__(a)
-
- a
➠operator.__neg__(a)
-
+ a
➠operator.__pos__(a)
-
a == b
➠operator.__eq__(a, b)
(includingobject.__eq__()
) -
a != b
➠operator.__ne__(a, b)
(includingobject.__ne__()
) -
a < b
➠operator.__lt__(a, b)
-
a <= b
➠operator.__le__(a, b)
-
a > b
➠operator.__gt__(a, b)
-
a >= b
➠operator.__ge__(a, b)
-
a is b
➠operator.is_(a, b)
-
a is not b
➠operator.is_not(a, b)
-
not a
➠operator.not_(a)
-
a in b
➠operator.__contains__(b, a)
-
a not in b
➠operator.not_(operator.__contains__(b, a))
-
a or b
➠_temp if (_temp := a) else b
-
a and b
➠_temp if not (_temp := a) else b
-
import a.b
➠a = __import__('a.b', globals(), locals())
-
import a.b as c
➠c = __import__('a', globals(), locals(), ['b'], 0).b
-
from .a import b
➠b = __import__('a', globals(), locals(), ['b'], 1).b
-
from .a import b as c
➠c = __import__('a', globals(), locals(), ['b'], 1).b
-
assert ...
➠ see below (post) -
for ...
➠ see below (includingbuiltins.iter()
andbuiltins.next()
) -
pass
➠"pass"
-
with ...
➠ see below (post) -
async def ...
➠ see below (post) -
await ...
➠desugar.builtins._await(...)
-
async for
➠ see below (includingbuiltins.aiter()
andbuiltins.anext()
) -
async with
➠ see below (post) -
(c for b in a)
➠ see below (post) -
[c for b in a]
➠list(c for b in a)
-
{c for b in a}
➠set(c for b in a)
-
{c: d for b in a}
➠dict((c, d) for b in a)
-
[a, b]
➠list((a, b))
(includes iterable unpacking) -
{a, b}
➠set((a, b))
(includes iterable unpacking) -
(a, b)
) ➠(lambda *args: args)(a, b)
(includes iterable unpacking) -
{a: b, c: d}
) ➠dict(((a, b), (c, d)))
(include dictionary unpacking) -
@decorator
➠ see below (post) -
break
➠ see below (post) -
continue
➠ see below (post) -
else
clause onwhile
➠ see below (post) -
elif
andelse
clauses onif
➠ see below (post) -
else
clause ontry
➠ see below (post) -
finally
clause ontry
➠ see below (post) -
raise A from B
➠ see below (post) -
x[A, B]
➠type(x).__getitem__(x, (A, B))
-
x[A, B] = C
➠type(x).__setitem__(x, (A, B), C)
-
del x[A, B]
➠type(x).__delitem__(x, (A, B))
-
A:B:C
➠slice(A, B, C)
-
4+3j
➠complex(4, 3)
-
True
➠bool(1)
-
False
➠bool(0)
-
None
➠ see below (post) -
b"ABC"
➠bytes([65, 66, 67])
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"ABC"
➠bytes([65, 66, 67]).decode("utf-8")
-
...
➠Ellipsis
-
class A: ...
➠ see below (post).
;` ➠ newline plus proper indentation -
if ...: ...
➠ see below (post) -
a := b
see the post -
lambda a: b
➠ see below (post) -
global A; A = 42
➠getattr(dict, "__setitem__")(globals(), "A", 42)
-
del A
➠ see below (post)
assert a, b
➠
if __debug__:
if not a:
raise AssertionError(b)
assert a
➠
if __debug__:
if not a:
raise AssertionError
for a in b:
c
➠
_iter = iter(b)
while True:
try:
a = next(_iter)
except StopIteration:
break
else:
c
del _iter
for a in b:
c
else:
d
➠
_iter = iter(b)
_looping = True
while _looping:
try:
a = next(_iter)
except StopIteration:
_looping = False
continue
else:
c
else:
d
del _iter, _looping
with a as b:
c
➠
_enter = type(a).__enter__
_exit = type(a).__exit__
b = _enter(a)
try:
c
except:
if not _exit(a, *sys.exc_info()):
raise
else:
_exit(a, None, None, None)
async def spam():
...
➠
@types.coroutine
def spam():
...
async for a in b:
c
➠
_iter = aiter(b)
while True:
try:
a = await anext(_iter)
except StopAsyncIteration:
break
else:
c
del _iter
async for a in b:
c
else:
d
➠
_iter = aiter(b)
_looping = True
while _looping:
try:
a = await anext(_iter)
except StopAsyncIteration:
_looping = False
continue
else:
c
else:
d
del _iter, _looping
async with a as b:
c
➠
_enter = type(a).__aenter__
_exit = type(a).__aexit__
b = await _enter(a)
try:
c
except:
if not await _exit(a, *sys.exc_info()):
raise
else:
await _exit(a, None, None, None)
(c for b in a)
➠
def _gen_exp(_leftmost_iterable):
for b in _leftmost_iterable:
yield c
_gen_exp(a)
@decorator
def func():
...
➠
def func():
...
_temp_func_name = func
del func
func = decorator(_temp_func_name)
while x:
break
➠
class _BreakStatement(Exception):
pass
try:
while x:
raise _BreakStatement
except BreakStatement:
pass
while x:
continue
➠
class _ContinueStatement(Exception):
pass
while x:
try:
raise _ContinueStatement
except ContinueStatement:
pass
while x:
break
else:
...
➠
class _BreakStatement(Exception):
pass
try:
while x:
raise _BreakStatement
except _BreakStatement:
pass
else:
...
if A:
B
➠
class _Done(Exception):
pass
try:
while A:
B
raise _Done
except _Done:
pass
if A:
B
elif C:
D
else:
E
➠
_B_ran = _D_ran = False
if A:
_B_ran = True
B
if not _B_ran and C:
_D_ran = True
D
if not (_B_ran or _D_ran):
E
try:
A
except:
B
else:
C
➠
_A_finished = False
try:
A
_A_finished = True
except:
B
if _A_finished:
C
try:
A
except Exception:
B
finally:
C
➠
try:
try:
A
except Exception:
B
except BaseException:
C
raise
C
raise A from B
➠
_raise = A
if isinstance(_raise, type) and issubclass(_raise, BaseException):
_raise = _raise()
elif not isinstance(_raise, BaseException):
raise TypeError("exceptions must derive from BaseException")
_from = B
if isinstance(_from, type) and issubclass(_from, BaseException):
_from = _from()
if _from is not None:
_raise.__cause__ = _from
raise _raise
None
➠
def _None():
pass
_None()
class Example(SuperClass):
"""Docstring."""
a: int = 3
def c(self): return 42
➠
def _exec_Example(_ns):
_temp_ns = {}
_temp_ns["__module__"] = _ns["__module__"] = __name__
_temp_ns[__"qualname__"] = _ns["__qualname__"] = "Example"
_temp_ns["__doc__"] = _ns["__doc__"] = """Docstring."""
_temp_ns["__annotations__"] = _ns["__annotations__"] = {"a": int}
_temp_ns["a"] = _ns["a"] = 3
def _method_c(self):
return 42
_method_c.__name__ = "c"
_method_c.__qualname__ = "Example.c"
temp_ns["c"] = _ns["c"] = _method_c
del _method_c
def _class_Example():
# Resolving MRO entries.
bases = types.resolve_bases((SuperClass, ))
# Determining the appropriate metaclass **and**
# preparing the class namespace.
meta, ns, kwds = types.prepare_class("Example", bases)
# Executing the class body.
_exec_Example(ns)
# Creating the class object.
cls = meta("Example", bases, ns)
## Class decorators, if there were any.
## Make the namespace read-only.
cls.__dict__ = read_only_proxy(ns)
return cls
Example = _class_Example()
lambda A: B
➠
def _lambda(A):
return B
_lambda.__name__ = "<lambda>"
del A
➠
_DELETED = object()
# `del A`
A = _DELETED
# Referencing `A`
if A is _DELETED:
raise UnboundLocalError("cannot access local variable 'A' where it is not associated with a value")
try:
gettattr(globals(), "__delitem__")("A")
except KeyError:
raise NameError("name 'A' is not defined")
Taken from the keyword
module.
Nothing; all unravelled!
Taken from the token
module.