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What does “hashable” mean in Python?
... data structures use the hash value internally.
All of Python’s immutable built-in objects are hashable, while no mutable containers (such as lists or dictionaries) are. Objects which are instances of user-defined classes are hashable by default; they all compare unequal, and their hash value...
Career day in kindergarten: how to demonstrate programming in 20 minutes? [closed]
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I've done this before.
I laid down a lot of paper towels on a table, and got out a loaf of (cheap) bread, a small tub of butter, a small jar of jelly, and a plastic butter knife.
I said to the kids, "How many of you think computers are smart?" Most of them raised their hands. I said,...
Why should you use an ORM? [closed]
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Making data access more abstract and portable. ORM implementation classes know how to write vendor-specific SQL, so you don't have to.
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LINQ to Entities does not recognize the method
...ect(iv => iv.ITEMNMBR.Trim()).ToList();
I added a .ToList() before my table, this decouple the Entity and linq code, and avoid my next linq expression be translated
NOTE: this solution isn't optimal, because avoid entity filtering, and simply loads all table into memory
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Execute SQLite script
...script, I think this works well:
$ sqlite3 example.db 'SELECT * FROM some_table;'
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How do I enable EF migrations for multiple contexts to separate databases?
...les in the Migrations folder
In SSMS, delete the __MigrationHistory system table.
Creating the initial migration:
In Package Manager Console:
Enable-Migrations -EnableAutomaticMigrations -ContextTypeName
NamespaceOfContext.ContextA -ProjectName ProjectContextIsInIfNotMainOne
-StartupProjectName...
Using ECMAScript 6
...le using classes
ES6 is a fast moving target. Refer to the Compatibility Table to find features supported by transpilers such as Traceur and Babel and browser support. You can even expand the chart to see the test used to verify compatibility:
To try out bleeding edge ES6 in a browser try the ...
multiprocessing: How do I share a dict among multiple processes?
...re my own work that is faster than Manager's dict and is simpler and more stable than pyshmht library that uses tons of memory and doesn't work for Mac OS. Though my dict only works for plain strings and is immutable currently.
I use linear probing implementation and store keys and values pairs in a...
EC2 Can't resize volume after increasing size
...sired new space (if empty the whole space is reserved)
Hit a to make it bootable
Hit 1 and w to write changes
Reboot instance OR use partprobe (from the parted package) to tell the kernel about the new partition table
Log via SSH and run resize2fs /dev/xvde1
Finally check the new space running df -h...
What is the PostgreSQL equivalent for ISNULL()
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Use COALESCE() instead:
SELECT COALESCE(Field,'Empty') from Table;
It functions much like ISNULL, although provides more functionality. Coalesce will return the first non null value in the list. Thus:
SELECT COALESCE(null, null, 5);
returns 5, while
SELECT COALESCE(null, 2, 5);...