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Reading a huge .csv file
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You are reading all rows into a list, then processing that list. Don't do that.
Process your rows as you produce them. If you need to filter the data first, use a generator function:
import csv
def getstuff(filename, criterion):
with ...
What's the difference between lists and tuples?
.... A list on the other hand could be used to store multiple locations. Naturally one might want to add or remove locations from the list, so it makes sense that lists are mutable. On the other hand it doesn't make sense to add or remove items from an existing location - hence tuples are immutable.
T...
Creating JS object with Object.create(null)?
...t.create(null) doesn't inherit from anything and thus has no properties at all.
In other words: A javascript object inherits from Object by default, unless you explicitly create it with null as its prototype, like: Object.create(null).
{} would instead be equivalent to Object.create(Object.prototy...
Update MongoDB field using value of another field
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The best way to do this is in version 4.2+ which allows using of aggregation pipeline in the update document and the updateOne, updateMany or update collection method. Note that the latter has been deprecated in most if not all languages drivers.
MongoDB 4.2+
Version 4.2 ...
How to find out what type of a Mat object is with Mat::type() in OpenCV
...";
r += (chans+'0');
return r;
}
If M is a var of type Mat you can call it like so:
string ty = type2str( M.type() );
printf("Matrix: %s %dx%d \n", ty.c_str(), M.cols, M.rows );
Will output data such as:
Matrix: 8UC3 640x480
Matrix: 64FC1 3x2
Its worth noting that there are also Matr...
Chrome, Javascript, window.open in new tab
...pup’) by specifying options in the 3rd parameter
3. If the window.open call was not part of a user-initiated event, it’ll open in a new window.
4. A “user initiated event” does not have to the same function call – but it must originate in the function invoked by a user click
5. If a use...
Preferred way to create a Scala list
...do so with a tail-recursive function, foldLeft, or something else is not really relevant.
If you get the elements in the same order you use them, then a ListBuffer is most likely a preferable choice, if performance is critical.
But, if you are not on a critical path and the input is low enough, yo...
“Incorrect string value” when trying to insert UTF-8 into MySQL via JDBC?
...ter you can change the column encoding from utf8 to utf8mb4. This encoding allows storage of characters that occupy 4 bytes in UTF-8.
You may also have to set the server property character_set_server to utf8mb4 in the MySQL configuration file. It seems that Connector/J defaults to 3-byte Unicode ot...
Pandas - How to flatten a hierarchical index in columns
..., but leaves behind column names which are difficult to access programmatically and are not queriable
– dmeu
Jun 29 '17 at 8:53
1
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Python constructors and __init__
Why are constructors indeed called "Constructors"? What is their purpose and how are they different from methods in a class?
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