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Get statistics for each group (such as count, mean, etc) using pandas GroupBy?
...ead of a Series) so you can do:
df.groupby(['col1', 'col2']).size().reset_index(name='counts')
If you want to find out how to calculate the row counts and other statistics for each group continue reading below.
Detailed example:
Consider the following example dataframe:
In [2]: df
Out[2]:...
What rules does Pandas use to generate a view vs a copy?
...is provided, it will modify in-place; only some operations support this
An indexer that sets, e.g. .loc/.iloc/.iat/.at will set inplace.
An indexer that gets on a single-dtyped object is almost always a view (depending on the memory layout it may not be that's why this is not reliable). This is main...
使用 XML 和 Web 服务 · App Inventor 2 中文网
...phabetical order by tag, regardless of their order in the original input sequence. Each pair consists of the tag, together with the decoding of the data delimited by that tag. As this example shows, if the items delimited by the tag are themselves XML-delimited text, then the data items for the p...
How do I use HTML as the view engine in Express?
...imple change from the seed and created the corresponding .html files (e.g. index.html).
16 Answers
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Which is faster/best? SELECT * or SELECT column1, colum2, column3, etc
...is that it raises the probability that SQL Server can access the data from indexes rather than querying the table data.
Here's a post I wrote about it: The real reason select queries are bad index coverage
It's also less fragile to change, since any code that consumes the data will be getting t...
How to create a directory in Java?
...
-1: That is actually a really bad technique to create a directory. The access to the FS is not reserved to a dedicated resource. Between if(!theDir.exists()) and theDir.mkdir() the status could have changed, as well as it could change in between not creating the di...
How to upper case every first letter of word in a string? [duplicate]
...
@kd i tryed google.at/search?q=java+word+uppercase thxn anyway
– Chris
Jul 19 '09 at 13:17
1
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Replace values in list using Python [duplicate]
...oesn't actually save time:
items = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
for index, item in enumerate(items):
if not (item % 2):
items[index] = None
Here are (Python 3.6.3) timings demonstrating the non-timesave:
In [1]: %%timeit
...: items = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
......
ActiveRecord.find(array_of_ids), preserving order
...
Oddly, no one has suggested something like this:
index = Something.find(array_of_ids).group_by(&:id)
array_of_ids.map { |i| index[i].first }
As efficient as it gets besides letting SQL backend do it.
Edit: To improve on my own answer, you can also do it like this:
S...
Oracle Differences between NVL and Coalesce
...on of branch filters when search contains comparison of nvl result with an indexed column.
create table tt(a, b) as
select level, mod(level,10)
from dual
connect by level<=1e4;
alter table tt add constraint ix_tt_a primary key(a);
create index ix_tt_b on tt(b);
explain plan for
select * from t...