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'and' (boolean) vs '&' (bitwise) - Why difference in behavior with lists vs numpy arrays?
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and tests whether both expressions are logically True while & (when used with True/False values) tests if both are True.
In Python, empty built-in objects are typically treated as logically False while non-empty built-ins are logically True. This facilitates the c...
Deprecated: mysql_connect()
...ay
mysqli_query($connection, 'CREATE TEMPORARY TABLE `table`');
Turn off all deprecated warnings including them from mysql_*:
<?php
error_reporting(E_ALL ^ E_DEPRECATED);
The Exact file and line location which needs to be replaced is "/System/Startup.php > line: 2 " error_reporting(E_All)...
How to list the contents of a package using YUM?
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There is a package called yum-utils that builds on YUM and contains a tool called repoquery that can do this.
$ repoquery --help | grep -E "list\ files"
-l, --list list files in this package/group
Combined into one example:
$ r...
What do the terms “CPU bound” and “I/O bound” mean?
...U (doing calculations). A program that computes new digits of π will typically be CPU-bound, it's just crunching numbers.
A program is I/O bound if it would go faster if the I/O subsystem was faster. Which exact I/O system is meant can vary; I typically associate it with disk, but of course networ...
Disable assertions in Python
...trate each.
For the whole process
Using the -O flag (capital O) disables all assert statements in a process.
For example:
$ python -Oc "assert False"
$ python -c "assert False"
Traceback (most recent call last):
File "<string>", line 1, in <module>
AssertionError
Note that by di...
Why does += behave unexpectedly on lists?
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The general answer is that += tries to call the __iadd__ special method, and if that isn't available it tries to use __add__ instead. So the issue is with the difference between these special methods.
The __iadd__ special method is for an in-place addition, that i...
Comma in C/C++ macro
...his is also a problem for square brackets and braces, even though those usually occur as balanced pairs.) You can enclose the macro argument in parentheses:
FOO((std::map<int, int>), map_var);
The problem is then that the parameter remains parenthesized inside the macro expansion, which pr...
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.al
I just discovered a logical bug in my code which was causing all sorts of problems. I was inadvertently doing a bitwise AND instead of a logical AND .
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Is it worth using Python's re.compile?
...uick glance at the actual Python 2.5 library code, I see that Python internally compiles AND CACHES regexes whenever you use them anyway (including calls to re.match()), so you're really only changing WHEN the regex gets compiled, and shouldn't be saving much time at all - only the time it takes to ...
How to delete or add column in SQLITE?
...upports a limited subset of ALTER TABLE. The ALTER TABLE command in SQLite allows the user to rename a table or to add a new column to an existing table. It is not possible to rename a column, remove a column, or add or remove constraints from a table.
You can:
create new table as the one you ar...