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...lambda s: zip(*s). That transformation also defines a matrix transpose or an equivalent row/column swap for tables defined as lists of tuples. The latter transformation is commonly used when reading data files with records as rows and fields as columns. For example, the code: date, rain, high, low = zip(*csv.reader(file("weather.csv"))) rearranges columnar data so that each field is collected into individual tuples for straightforward looping and summarization: print "Total rainfall", sum(...
...lambda e: isinstance(e, TypeError)) >>> traceback.print_exception(type_errors) | ExceptionGroup: one (2 sub-exceptions) +-+---------------- 1 ---------------- | TypeError: 1 +---------------- 2 ---------------- | ExceptionGroup: two (1 sub-exception) +-+---------------- 1 ---------------- | TypeError: 2 +------------------------------------ >>> The match condition is also applied to interior nodes (the exception groups), and a match causes the w...
...lambda *a: None, 'addhook': lambda *a: None}) Multiple layers of protection already exist for monkey patching attacks against either sys or audit, but assignments or insertions to sys.modules are not audited. This idea is rejected because it makes it trivial to suppress all calls to audit. Flag in sys.flags to indicate "audited" mode The proposal is to add a value in sys.flags to indicate when Python is running in a "secure" or "audited" mode. This would allow applications to detect when some...
...lambda: None) try: traditional-for VAR in _iter: LOOP-BODY else: ELSE-BODY finally: _iterclose(_iter) where the "traditional-for statement" here is meant as a shorthand for the classic 3.5-and-earlier for loop semantics. Besides the top-level for statement, Python also contains several other places where iterators are consumed. For consistency, these should call __iterclose__ as well using semantics equivalent to the above. This includes: for loops inside comprehens...
...lambda self, ob: self.push(ob)) when(IStack.pop, (Stack,))(lambda self, ob: self.pop()) That is, calling IStack.push() or IStack.pop() on an instance of any subclass of Stack, will simply delegate to the actual push() or pop() methods thereof. For the sake of efficiency, calling IStack(s) where s is an instance of Stack, may return s rather than an IStack adapter. (Note that calling IStack(x) where x is already an IStack adapter will always return x unchanged; this is an additional optimizatio...
...lambda: 666 If main.py is run under Python 2.2 (or before), 666 is printed. But under the proposal, __builtin__.pachinko doesn't exist at the time main's __dict__ is initialized. When the function object for f is created, main.__dict__ grows a pachinko cell mapping to two NULLs. When cheat() is called, __builtin__.__dict__ grows a pachinko cell too, but main.__dict__ doesn't know-- and will never know --about that. When f's return stmt references pachinko, in will still find the double-NULL...
...lambdas required in typical callback programming. This convention specifically does not support keyword arguments. Keyword arguments are used to pass optional extra information about the callback. This allows graceful evolution of the API without having to worry about whether a keyword might be significant to a callee somewhere. If you have a callback that must be called with a keyword argument, you can use a lambda. For example: loop.call_soon(lambda: foo('abc', repeat=42)) Coroutines a...
...lambda: '__getattribute__' a = A() assert a() == '__call__' assert a.__call__() == '__getattribute__' In any case, with the renaming of __builtin__.super to __builtin__.__super__ this issue goes away entirely. Reference Implementation It is impossible to implement the above specification entirely in Python. This reference implementation has the following differences to the specification: New super semantics are implemented using bytecode hacking. Assignment to super is not a SyntaxError. A...
...lambda cls: cls.__name__ class ex_2: "Serious order disagreement" #From Guido class O: pass class X(O): pass class Y(O): pass class A(X,Y): pass class B(Y,X): pass try: class Z(A,B): pass #creates Z(A,B) in Python 2.2 except TypeError: pass # Z(A,B) cannot be created in Python 2.3 class ex_5: "My first example" class O: pass class F(O): pass class E(O): pass class D(O): pass class C(D,F): pass class...
...lambda *args: None))) '(*args)' >>> str(Signature()) '()' Parameter Object Python's expressive syntax means functions can accept many different kinds of parameters with many subtle semantic differences. We propose a rich Parameter object designed to represent any possible function parameter. A Parameter object has the following public attributes and methods: name : str The name of the parameter as a string. Must be a valid python identifier name (with the exception of POSITIONAL...
...lambda: ClassNamespace(cls) class Example: pass class ExtendedExample(namespace=extend(Example)): a = 1 b = 2 c = 3 >>> Example.a, Example.b, Example.c (1, 2, 3) Rejected Design Options Calling __autodecorate__ from type.__init__ Calling the new hook automatically from type.__init__, would achieve most of the goals of this PEP. However, using that approach would mean that __autodecorate__ implementations would be unable to call any methods that relied on the __cl...
...lambda has restrictions compared to def, so does a generator expression have restrictions compared to a generator function. In many cases, the transformation to full generator function will be trivially easy, and may improve structural clarity. Explanation of generators, iterators, and StopIteration The proposal does not change the relationship between generators and iterators: a generator object is still an iterator, and not all iterators are generators. Generators have additional methods t...
...Lambda binding solved?) (Rafael Bracho) https://legacy.python.org/search/hypermail/python-1994q1/0301.html [2](1, 2) Extended Function syntax (Just van Rossum) https://mail.python.org/pipermail/python-dev/2003-February/032764.html [3]Closure semantics (Guido van Rossum) https://mail.python.org/pipermail/python-dev/2003-October/039214.html [4](1, 2) Better Control of Nested Lexical Scopes (Almann T. Goo) https://mail.python.org/pipermail/python-dev/2006-February/061568.html [5...
...Lambdas may have to be parenthesized PEP 308 [NO] In order to get rid of the confusion between __builtin__ and __builtins__, it was decided to rename __builtin__ (the module) to builtins, and to leave __builtins__ (the sandbox hook) alone. [33] [34] [done] Attributes on functions of the form func_whatever will be renamed __whatever__ [17] [done] Set literals and comprehensions [19] [20] [done] {x} means set([x]); {x, y} means set([x, y]). {F(x) for x in S if P(x)} means set(F(x) for x in S if ...
...lambda [tim] > Think this might actually happen <wink>? [Guido] > Perhaps... Ah! Newcomers should be told that this is Guido's subtle way of saying he's in doubt about scraping together September rent money. Enough said. emailing-cash-and-lots-of-it-ly y'rs - tim Neutral testimony... Subject: Re: Just Say No to // From: Johann Hibschman <@physics.berkeley.edu> Date: 06 Sep 1998 22:15:39 -0700 To: python-list@cwi.nl "M.-A. Lemburg" <@lemburg.c...
...lambda *x:map(f, *x), a, b) More generally,: def ~f(*x): return map(f, *x) def ~~f(*x): return map(~f, *x) ... Elementwise format operator (with broadcasting): a = [1,2,3,4,5] print ["%5d "] ~% a a = [[1,2],[3,4]] print ["%5d "] ~~% a Rich comparison: [1, 2, 3] ~< [3, 2, 1] # [1, 0, 0] [1, 2, 3] ~== [3, 2, 1] # [0, 1, 0] Rich indexing: [a, b, c, d] ~[2, 3, 1] # [c, d, b] Tuple flattening: a = (1,2); b = (3,4) f(~a, ~b) # f(1,2,3,4) Copy operator: a ~= b ...
...lambda k, v1, v2: v2): # implementation left as an exercise to the reader Advantages Most of the same advantages of the method solutions above. Doesn't require a subclass to implement alternative behavior on collisions, just a function. Disadvantages May not be important enough to be a builtin. Hard to override behavior if you need something like "first wins", without losing the ability to process arbitrary keyword arguments. Examples The authors of this PEP did a survey of thir...
...lambda self: self.x + 1}) Is equivalent to: @dataclass class C: x: int y: 'typing.Any' z: int = 5 def add_one(self): return self.x + 1 replace(instance, **changes): Creates a new object of the same type of instance, replacing fields with values from changes. If instance is not a Data Class, raises TypeError. If values in changes do not specify fields, raises TypeError. The newly returned object is created by calling the __init__ method of the Data Class. This ensur...
...lambda : 0) name: str Runtime behavior At runtime, the dataclass_transform decorator's only effect is to set a string attribute named __dataclass_transform__ on the decorated function or class to support introspection. The value of the attribute should be a dict mapping the names of the dataclass_transform parameters to their values. For example: { "eq_default": True, "order_default": False, "kw_only_default": False, "field_descriptors": () } Dataclass semantics The following...
...lambda. The second is built-in functions such as len, isinstance or numpy.dot. These are implemented in C. These two classes are implemented completely independently and have different functionality. In particular, it is currently not possible to implement a function efficiently in C (only built-in functions can do that) while still allowing introspection like inspect.signature or inspect.getsourcefile (only Python functions can do that). This is a problem for projects like Cython [1] that want ...