大约有 40,000 项符合查询结果（耗时：0.0421秒） [XML]
From an array of objects, extract value of a property as array
...
Check out Lodash's _.pluck() function or Underscore's _.pluck() function. Both do exactly what you want in a single function call!
var result = _.pluck(objArray, 'foo');
Update: _.pluck() has been removed as of Lodash v4.0.0, in favour of _...
Python Linked List
...tains a cargo object and a reference to a linked list.
class Node:
def __init__(self, cargo=None, next=None):
self.car = cargo
self.cdr = next
def __str__(self):
return str(self.car)
def display(lst):
if lst:
w("%s " % lst)
display(lst.cdr)
else:
w("nil\n")
...
Python (and Python C API): __new__ versus __init__
The question I'm about to ask seems to be a duplicate of Python's use of __new__ and __init__? , but regardless, it's still unclear to me exactly what the practical difference between __new__ and __init__ is.
...
Get last result in interactive Python shell
...
Underscore.
>>> 5+5
10
>>> _
10
>>> _ + 5
15
>>> _
15
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How to implement a binary tree?
...plementation of binary search tree.
#!/usr/bin/python
class Node:
def __init__(self, val):
self.l = None
self.r = None
self.v = val
class Tree:
def __init__(self):
self.root = None
def getRoot(self):
return self.root
def add(self, val):
...
MySQL: What's the difference between float and double?
...00002 | 1.6900000000 |
This is using MySQL 6.7
Query:
SELECT
float_1 + float_2 as 'float add',
double_1 + double_2 as 'double add',
decimal_1 + decimal_2 as 'decimal add',
float_1 * float_2 as 'float multiply',
double_1 * double_2 as 'double multiply',
decimal_1 * decim...
Django select only rows with duplicate field values
...values('name')
.annotate(Count('id'))
.order_by()
.filter(id__count__gt=1)
This is as close as you can get with Django. The problem is that this will return a ValuesQuerySet with only name and count. However, you can then use this to construct a regula...
How to serialize SqlAlchemy result to JSON?
...(json.JSONEncoder):
def default(self, obj):
if isinstance(obj.__class__, DeclarativeMeta):
# an SQLAlchemy class
fields = {}
for field in [x for x in dir(obj) if not x.startswith('_') and x != 'metadata']:
data = obj.__getattribute__(f...
Pickle or json?
...ccf1b3fa91f4399902bb534/raw/03e8dbab11b5605bc572bc117c8ac34cfa959a70/pickle_vs_json.py
python pickle_vs_json.py
Results with python 2.7 on a decent 2015 Xeon processor:
Dir Entries Method Time Length
dump 10 JSON 0.017 1484510
load 10 JSON 0.375 -
dump 10 Pickle 0.011 ...
sql “LIKE” equivalent in django query
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Use __contains or __icontains (case-insensitive):
result = table.objects.filter(string__contains='pattern')
The SQL equivalent is
SELECT ... WHERE string LIKE '%pattern%';
...