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List of lists changes reflected across sublists unexpectedly
...s visible via all three references to it:
x = [1] * 4
l = [x] * 3
print(f"id(x): {id(x)}")
# id(x): 140560897920048
print(
f"id(l[0]): {id(l[0])}\n"
f"id(l[1]): {id(l[1])}\n"
f"id(l[2]): {id(l[2])}"
)
# id(l[0]): 140560897920048
# id(l[1]): 140560897920048
# id(l[2]): 140560897920048
x...
Why does the C++ map type argument require an empty constructor when using []?
... Why is that std::<map>::value_type there in the insert call?
– thomthom
May 6 '15 at 11:53
...
datetime dtypes in pandas read_csv
...way of solving this
The pandas.read_csv() function has a keyword argument called parse_dates
Using this you can on the fly convert strings, floats or integers into datetimes using the default date_parser (dateutil.parser.parser)
headers = ['col1', 'col2', 'col3', 'col4']
dtypes = {'col1': 'str', ...
Get the latest record from mongodb collection
...oDB are B-Trees. Searching a B-Tree is a O(logN) operation, so even find({_id:...}) will not provide constant time, O(1) responses.
That stated, you can also sort by the _id if you are using ObjectId for you IDs. See here for details. Of course, even that is only good to the last second.
You may t...
Operation on every pair of element in a list
...Odd, when I run itertools.product(my_list, 2), it complains that int isn't callable. Works once I change it to: itertools.product(my_list, repeat=2)
– ojrac
Jun 3 '09 at 0:34
...
JS Client-Side Exif Orientation: Rotate and Mirror JPEG Images
...ion extraction demo.
function resetOrientation(srcBase64, srcOrientation, callback) {
var img = new Image();
img.onload = function() {
var width = img.width,
height = img.height,
canvas = document.createElement('canvas'),
ctx = canvas.getContext("2d");
// s...
Ignoring an already checked-in directory's contents?
...
For a subdirectory called blah/ added to git, both of the following seem to work to ignore new files in blah/. Added to .gitignore:
blah
blah/*
share
|
...
MySQL Error 1093 - Can't specify target table for update in FROM clause
...n case certain operations are carried out, merging cannot happen. E.g. provide the derived dummy table with a LIMIT (to inifity) and the error will never occur. That's pretty hackish though and there is still the risk that future versions of MySQL will support merging queries with LIMIT after all.
...
Rails 3: Get Random Record
... on an indexed column (PostgreSQL syntax):
select *
from my_table
where id >= trunc(
random() * (select max(id) from my_table) + 1
)
order by id
limit 1;
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improve this answer
...
Switching the order of block elements with CSS [duplicate]
...ly need to support a single modern browser: Mobile Safari.
See: http://jsfiddle.net/thirtydot/hLUHL/
You can remove the -moz- prefixed properties if you like, I just left them in for future readers.
#blockContainer {
display: -webkit-box;
display: -moz-box;
disp...