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Slicing of a NumPy 2d array, or how do I extract an mxm submatrix from an nxn array (n>m)?
...ce a NumPy nxn array. I want to extract an arbitrary selection of m rows and columns of that array (i.e. without any pattern in the numbers of rows/columns), making it a new, mxm array. For this example let us say the array is 4x4 and I want to extract a 2x2 array from it.
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psycopg2: insert multiple rows with one query
...e which allows an iterator yielding strings to be read like a file. We can convert each input record to a string using a generator expression. So the solution would be
args = [(1,2), (3,4), (5,6)]
f = IteratorFile(("{}\t{}".format(x[0], x[1]) for x in args))
cursor.copy_from(f, 'table_name', column...
PSQLException: current transaction is aborted, commands ignored until end of transaction block
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I got this error using Java and PostgreSQL doing an insert on a table. I will illustrate how you can reproduce this error:
org.postgresql.util.PSQLException: ERROR:
current transaction is aborted, commands ignored until end of transaction block
Summa...
Test if a command outputs an empty string
...ll do something like this:
run a command
buffer its entire output in RAM
convert the output into a huge single-line string
compare that string to an empty string
What I would suggest doing instead would be:
run a command
count the characters in its output without storing them
or even better ...
How to access object attribute given string corresponding to name of that attribute
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There are built-in functions called getattr and setattr
getattr(object, attrname)
setattr(object, attrname, value)
In this case
x = getattr(t, 'attr1')
setattr(t, 'attr1', 21)
share
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Specify format for input arguments argparse python
... can take any callable that takes a single string argument and returns the converted value
You could do something like:
def valid_date(s):
try:
return datetime.strptime(s, "%Y-%m-%d")
except ValueError:
msg = "Not a valid date: '{0}'.".format(s)
raise argparse.Argu...
SQL WHERE.. IN clause multiple columns
...
While this would work, it converts the uncorrelated query in the question into a correlated query. Unless the query optimizer is clever, this might give you O(n^2) performance :-(. But maybe I'm underestimating the optimizer...
–...
Use tab to indent in textarea
... spaces instead of a tab? I tried doing   four times but it still converted it into a single space.
– jiaweizhang
Apr 18 '16 at 0:05
6
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SQLite select where empty?
...n I select records where some_column is empty?
Empty counts as both NULL and "".
4 Answers
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jQuery - Add ID instead of Class
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Im doing this in coffeescript
booking_module_time_clock_convert_id = () ->
if $('.booking_module_time_clock').length
idnumber = 1
for a in $('.booking_module_time_clock')
elementID = $(a).attr("id")
$(a).attr( 'id', "#{elementID}_#{idnumber}" )
idnum...