It is highly probable that re.finditer uses fairly minimal memory overhead. def split_iter(string): return (x.group(0) for x in re.finditer(r”[A-Za-z’]+”, string)) Demo: >>> list( split_iter(“A programmer’s RegEx test.”) ) [‘A’, “programmer’s”, ‘RegEx’, ‘test’] edit: I have just confirmed that this takes constant memory in python 3.2.1, assuming my testing methodology was correct. I created a string … Read more
Quick answer: Doing list() around a generator expression is (almost) exactly equivalent to having [] brackets around it. So yeah, you can do >>> list((x for x in string.letters if x in (y for y in “BigMan on campus”))) But you can just as well do >>> [x for x in string.letters if x in … Read more
Generators exist in C++, just under another name: Input Iterators. For example, reading from std::cin is similar to having a generator of char. You simply need to understand what a generator does: there is a blob of data: the local variables define a state there is an init method there is a “next” method there … Read more
I see many answers suggesting itertools.tee, but that’s ignoring one crucial warning in the docs for it: This itertool may require significant auxiliary storage (depending on how much temporary data needs to be stored). In general, if one iterator uses most or all of the data before another iterator starts, it is faster to use … Read more
To understand what yield does, you must understand what generators are. And before you can understand generators, you must understand iterables. Iterables When you create a list, you can read its items one by one. Reading its items one by one is called iteration: >>> mylist = [1, 2, 3] >>> for i in mylist: … Read more
Yes, or next(gen) in 2.6+.
itertools provides three infinite iterators: count(start=0, step=1): 0, 1, 2, 3, 4, … cycle(p): p[0], p[1], …, p[-1], p[0], … repeat(x, times=∞): x, x, x, x, … I don’t know of any others in the standard library. Since you asked for a one-liner: __import__(“itertools”).count()
the Microsoft XSD inference tool is a good, free solution. Many XML editing tools, such as XmlSpy (mentioned by @Garth Gilmour) or OxygenXML Editor also have that feature. They’re rather expensive, though. BizTalk Server also has an XSD inferring tool as well. edit: I just discovered the .net XmlSchemaInference class, so if you’re using .net … Read more
Simply call list on the generator. lst = list(gen) lst Be aware that this affects the generator which will not return any further items. You also cannot directly call list in IPython, as it conflicts with a command for listing lines of code. Tested on this file: def gen(): yield 1 yield 2 yield 3 … Read more
I’ll start with generators, seeing as they’re the simplest case. As @zvolkov mentioned, they’re functions/objects that can be repeatedly called without returning, but when called will return (yield) a value and then suspend their execution. When they’re called again, they will start up from where they last suspended execution and do their thing again. A … Read more