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
Calls to itertools.imap() in Python 2 or map() in Python 3 can be replaced by equivalent generator expressions: sum(1 for dummy in it) This also uses a lazy generator, so it avoids materializing a full list of all iterator elements in memory.
The generator is expanded at the time of the function call, as you can easily check: def f(*args): print(args) foo = [‘foo’, ‘bar’, ‘baz’] gen = (f for f in foo) f(*gen) will print (‘foo’, ‘bar’, ‘baz’)
You could use rest parameters … and check the length of the rest array for another calling of the generator function* flat(a, …r) { if (Array.isArray(a)) { yield* flat(…a); } else { yield ‘foo’ + a; } if (r.length) { yield* flat(…r); } } var obj = [1, 2, 3, [4, 5, [6, 7, 8], … Read more
Because ending the generator is not a common event (I know it will always happen, but it only happens once). Throwing the exception is considered expensive. If an event is going to succeed 99% of the time and fail 1%, using try/except can be much faster than checking if it’s okay to access that data … Read more
The following is from the CMake Source (version 2.8.4: cmake.cxx: starting line 2039): // Try to find the newest VS installed on the computer and // use that as a default if -G is not specified std::string vsregBase = “[HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\VisualStudio\\”; struct VSRegistryEntryName { const char* MSVersion; const char* GeneratorName; }; VSRegistryEntryName version[] = { {“6.0”, … Read more
I have used the data generator in the past. May be worth a look. 3rd party edit If you do not register you can only generate 100 rows. Below you can find a sample how the interface looks today (october 2016)
The next method is defined as follows: 25.3.1.2 Generator.prototype.next ( value ) The next method performs the following steps: Let g be the this value. Return GeneratorResume(g, value). The GeneratorResume abstract operation uses value at step 10: 25.3.3.3 GeneratorResume ( generator, value ) The abstract operation GeneratorResume with arguments generator and value performs the following … Read more
The fastest way is by using itertools, especially chain and combinations: >>> from itertools import chain, combinations >>> i = set([1, 2, 3]) >>> for z in chain.from_iterable(combinations(i, r) for r in range(len(i)+1)): print z () (1,) (2,) (3,) (1, 2) (1, 3) (2, 3) (1, 2, 3) >>> If you need a generator just … Read more
I can’t help debug your code since you didn’t post it, but I abbreviated a custom data generator I wrote for a semantic segmentation project for you to use as a template: def generate_data(directory, batch_size): “””Replaces Keras’ native ImageDataGenerator.””” i = 0 file_list = os.listdir(directory) while True: image_batch = [] for b in range(batch_size): if … Read more