Use: gw_func_dict = dict((chr(2**i), func) for i, func in enumerate(gwfuncs[:8])) That’s the dict() function with a generator expression producing (key, value) pairs. Or, to put it generically, a dict comprehension of the form: {key_expr: value_expr for targets in iterable <additional loops or if expressions>} can always be made compatible with Python < 2.7 by using: … Read more
A dictionary comprehension can only ever produce one key-value pair per iteration. The trick then is to produce an extra loop to separate out the pairs: {k: v for e in wp_users for k, v in zip((‘ID’, ‘post_author’), e)} This is equivalent to: result = {} for e in wp_users: for k, v in zip((‘ID’, … Read more
The short form is as follows (called dict comprehension, as analogy to the list comprehension, set comprehension etc.): x = { row.SITE_NAME : row.LOOKUP_TABLE for row in cursor } so in general given some _container with some kind of elements and a function _value which for a given element returns the value that you want … Read more
{inner_k: myfunc(inner_v)} isn’t a dictionary comprehension. It’s just a dictionary. You’re probably looking for something like this instead: data = {outer_k: {inner_k: myfunc(inner_v) for inner_k, inner_v in outer_v.items()} for outer_k, outer_v in outer_dict.items()} For the sake of readability, don’t nest dictionary comprehensions and list comprehensions too much.
.items() will return (key, value) pairs that you can use to reconstruct a filtered dict using a list comprehension that is feed into the dict() constructor, that will accept an iterable of (key, value) tuples aka. our list comprehension: >>> d = dict(a=1, b=10, c=30, d=2) >>> d {‘a’: 1, ‘c’: 30, ‘b’: 10, ‘d’: … Read more
You are testing with way too small an input; while a dictionary comprehension doesn’t have as much of a performance advantage against a for loop when compared to a list comprehension, for realistic problem sizes it can and does beat for loops, especially when targeting a global name. Your input consists of just 3 key-value … Read more
Sorry, not possible. Dict literals and dict comprehensions map to the built-in dict type, in a way that’s hardcoded at the C level. That can’t be overridden. You can use this as an alternative, though: OrderedDict((i, i * i) for i in range(3)) Addendum: as of Python 3.6, all Python dictionaries are ordered. As of … Read more
You were close, try the snippet below: >>> my_dict = { … “keyA”: 1, … “keyB”: 2, … “keyC”: 3 … } >>> invalid = {“keyA”, “keyB”} >>> def without_keys(d, keys): … return {x: d[x] for x in d if x not in keys} >>> without_keys(my_dict, invalid) {‘keyC’: 3} Basically, the if k not in … Read more
You’ve already got it: A if test else B is a valid Python expression. The only problem with your dict comprehension as shown is that the place for an expression in a dict comprehension must have two expressions, separated by a colon: { (some_key if condition else default_key):(something_if_true if condition else something_if_false) for key, value … Read more
You can use a generator expression: tuple(i for i in (1, 2, 3)) but parentheses were already taken for … generator expressions.