大约有 42,000 项符合查询结果（耗时：0.0411秒） [XML]
[] and {} vs list() and dict(), which is better?
...gt;> from timeit import timeit
>>> timeit("[]")
0.040084982867934334
>>> timeit("list()")
0.17704233359267718
>>> timeit("{}")
0.033620194745424214
>>> timeit("dict()")
0.1821558326547077
and for non-empty:
>>> timeit("[1,2,3]")
0.24316302770330367
...
Cost of len() function
...
360
It's O(1) (constant time, not depending of actual length of the element - very fast) on every ...
PHP append one array to another (not array_push or +)
...
436
array_merge is the elegant way:
$a = array('a', 'b');
$b = array('c', 'd');
$merge = array_mer...
How to filter a dictionary according to an arbitrary condition function?
...
434
Nowadays, in Python 2.7 and up, you can use a dict comprehension:
{k: v for k, v in points.ite...
using awk with column value conditions
...
132
If you're looking for a particular string, put quotes around it:
awk '$1 == "findtext" {print ...
How to count the number of occurrences of an element in a List
...
341
I'm pretty sure the static frequency-method in Collections would come in handy here:
int occu...
How can I convert a dictionary into a list of tuples?
...
363
>>> d = { 'a': 1, 'b': 2, 'c': 3 }
>>> d.items()
[('a', 1), ('c', 3), ('b', ...
How to profile a bash shell script slow startup?
My bash shell takes up to 3-4 seconds to start up, while if I start it with --norc it runs immediately.
7 Answers
...
Change the name of a key in dictionary
...elete dictionary[old_key].
>>> dictionary = { 1: 'one', 2:'two', 3:'three' }
>>> dictionary['ONE'] = dictionary.pop(1)
>>> dictionary
{2: 'two', 3: 'three', 'ONE': 'one'}
>>> dictionary['ONE'] = dictionary.pop(1)
Traceback (most recent call last):
File "<inp...
C#位运算符（C#按位与、按位或 等） - 更多技术 - 清泛网 - 专注C/C++及内核技术
...如：10010001（二进制）&11110000等于10010000（二进制）。
3、位逻辑或运算
位逻辑或运算将两个运算对象按位进行或运算。或运算的规则是：1或1等1，1或0等于1，
0或0等于0。比如10010001（二进制）| 11110000（二进制）等于11110001...