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Transaction isolation levels relation with locks on table
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I want to understand the lock each transaction isolation takes on the table
For example, you have 3 concurrent processes A, B and C. A starts a transaction, writes data and commit/rollback (depending on results). B just executes a SELECT st...
Iterating through directories with Python
I need to iterate through the subdirectories of a given directory and search for files. If I get a file I have to open it and change the content and replace it with my own lines.
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What does Expression.Quote() do that Expression.Constant() can’t already do?
...e quote operator is an operator which induces closure semantics on its operand. Constants are just values.
Quotes and constants have different meanings and therefore have different representations in an expression tree. Having the same representation for two very different things is extremely confu...
Django: Why do some model fields clash with each other?
...Jul 17 '09 at 10:20
Daniel RosemanDaniel Roseman
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JavaScript hard refresh of current page
...page via JavaScript?
Hard refresh means getting a fresh copy of the page AND refresh all the external resources (images, JavaScript, CSS, etc.).
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How to display request headers with command line curl
Command line curl can display response header by using -D option, but I want to see what request header it is sending. How can I do that?
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Why use symbols as hash keys in Ruby?
... basically "immutable strings" .. that means that they can not be changed, and it implies that the same symbol when referenced many times throughout your source code, is always stored as the same entity, e.g. has the same object id.
Strings on the other hand are mutable, they can be changed anytim...
Ruby on Rails patterns - decorator vs presenter
...all sorts of talk lately in the Ruby on Rails community about decorators and presenters.
2 Answers
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Filter dict to contain only certain keys?
...nary comprehension.
If you use a version which lacks them (ie Python 2.6 and earlier), make it dict((your_key, old_dict[your_key]) for ...). It's the same, though uglier.
Note that this, unlike jnnnnn's version, has stable performance (depends only on number of your_keys) for old_dicts of any siz...
Convert base-2 binary number string to int
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You use the built-in int function, and pass it the base of the input number, i.e. 2 for a binary number:
>>> int('11111111', 2)
255
Here is documentation for python2, and for python3.
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