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How does Rails keep track of which migrations have run for a database?
...
Rails creates a table in your database called schema_migrations to keep track of which migrations have run.
The table contains a single column, version. When Rails runs a migration, it takes the leading digits in the migration's file name and inserts a row for that "version",...
How to read a large file - line by line?
...object, Python looks up in the list of object methods a special one called __iter__, which tells it what to do. File objects define this special method to return an iterator over the lines. (Roughly.)
– Katriel
Feb 10 '15 at 12:14
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How to list all users in a Linux group?
...rs;
my $usertext = `getent passwd`;
my @users = $usertext =~ /^([a-zA-Z0-9_-]+):/gm;
foreach my $userid (@users)
{
my $usergrouptext = `id -Gn $userid`;
my @grouplist = split(' ',$usergrouptext);
foreach my $group (@grouplist)
{
$groupmembers{$group}->{$userid} = 1;
...
Convert an NSURL to an NSString
...[myURL absoluteString]; But I had met this error and xcode was crashed. -[__NSCFString absoluteString]: unrecognized selector sent to instance 0x791a18e0
– Võ Mai Trinh
Jun 22 '15 at 9:39
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How to use/install gcc on Mac OS X 10.8 / Xcode 4.4
... Apple LLVM version 6.0 (clang-600.0.51) (based on LLVM 3.5svn) Target: x86_64-apple-darwin14.0.0 Thread model: posix So am I using gcc?
– Thomas
Dec 14 '14 at 16:11
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Android file chooser [closed]
...tent in an Intent.createChooser() like this:
private static final int FILE_SELECT_CODE = 0;
private void showFileChooser() {
Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
intent.setType("*/*");
intent.addCategory(Intent.CATEGORY_OPENABLE);
try {
startActivityFor...
How to use “raise” keyword in Python [duplicate]
...dler, so that it can be handled further up the call stack.
try:
generate_exception()
except SomeException as e:
if not can_handle(e):
raise
handle_exception(e)
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Detect if a NumPy array contains at least one non-numeric value?
... numba
import numpy as np
NAN = float("nan")
@numba.njit(nogil=True)
def _any_nans(a):
for x in a:
if np.isnan(x): return True
return False
@numba.jit
def any_nans(a):
if not a.dtype.kind=='f': return False
return _any_nans(a.flat)
array1M = np.random.rand(1000000)
assert...
Define variable to use with IN operator (T-SQL)
...T @sql = 'SELECT * FROM myTable WHERE myColumn in (' + @list + ')'
exec sp_executeSQL @sql
3) A possible third option is table variables. If you have SQl Server 2005 you can use a table variable. If your on Sql Server 2008 you can even pass whole table variables in as a parameter to stored proced...
Utils to read resource text file to String (Java) [closed]
...urce("foo.txt");
String text = Resources.toString(url, StandardCharsets.UTF_8);
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