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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]
......
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...
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...
Is there a performance difference between CTE , Sub-Query, Temporary Table or Table Variable?
...hints, restructure the query, update statistics, use temporary tables, add indexes, and so on to get better performance.
As for your question. The performance of CTEs and subqueries should, in theory, be the same since both provide the same information to the query optimizer. One difference is th...
Naming returned columns in Pandas aggregate function? [duplicate]
...
This will drop the outermost level from the hierarchical column index:
df = data.groupby(...).agg(...)
df.columns = df.columns.droplevel(0)
If you'd like to keep the outermost level, you can use the ravel() function on the multi-level column to form new labels:
df.columns = ["_".join(...
Easiest way to check for an index or a key in an array?
...
To check if the element is set (applies to both indexed and associative array)
[ ${array[key]+abc} ] && echo "exists"
Basically what ${array[key]+abc} does is
if array[key] is set, return abc
if array[key] is not set, return nothing
References:
See Parame...
Why is the order in dictionaries and sets arbitrary?
... if two objects have the same hash they can be unequal.)
You then make in index by taking the modulus by the array length:
hash(4) % len(storage) = index 2
This makes it really fast to access elements.
Hashes are only most of the story, as hash(n) % len(storage) and hash(m) % len(storage) can r...
MD5 algorithm in Objective-C
... char *resultData = malloc(CC_MD5_DIGEST_LENGTH * 2 + 1);
for (uint index = 0; index < CC_MD5_DIGEST_LENGTH; index++) {
resultData[index * 2] = HexEncodeChars[(result[index] >> 4)];
resultData[index * 2 + 1] = HexEncodeChars[(result[index] % 0x10)];
}
resultDa...
GroupBy pandas DataFrame and select most common value
...,'NY']})
source.groupby(['Country','City']).agg(lambda x:x.value_counts().index[0])
In case you are wondering about performing other agg functions in the .agg()
try this.
# Let's add a new col, account
source['account'] = [1,2,3,3]
source.groupby(['Country','City']).agg(mod = ('Short name', \...
Getting JavaScript object key list
...
you need to increment array index
– Vivek
Jul 14 '14 at 9:43
array inde...