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How to add column if not exists on PostgreSQL?
...statement:
DO $$
BEGIN
BEGIN
ALTER TABLE <table_name> ADD COLUMN <column_name> <column_type>;
EXCEPTION
WHEN duplicate_column THEN RAISE NOTICE 'column <column_name> already exists in <table_name>.';
END;
END;
$$
...
Override Python's 'in' operator?
...
MyClass.__contains__(self, item)
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Python debugging tips [closed]
...
PDB
You can use the pdb module, insert pdb.set_trace() anywhere and it will function as a breakpoint.
>>> import pdb
>>> a="a string"
>>> pdb.set_trace()
--Return--
> <stdin>(1)<module>()->None
(Pdb) p a
'a string'
(Pdb)
To...
Regular expression for letters, numbers and - _
...he pattern you want is something like (see it on rubular.com):
^[a-zA-Z0-9_.-]*$
Explanation:
^ is the beginning of the line anchor
$ is the end of the line anchor
[...] is a character class definition
* is "zero-or-more" repetition
Note that the literal dash - is the last character in the ch...
How to write header row with csv.DictWriter?
...od now available in 2.7 / 3.2:
from collections import OrderedDict
ordered_fieldnames = OrderedDict([('field1',None),('field2',None)])
with open(outfile,'wb') as fou:
dw = csv.DictWriter(fou, delimiter='\t', fieldnames=ordered_fieldnames)
dw.writeheader()
# continue on to write data
...
How to iterate for loop in reverse order in swift?
... an array with one trillion Ints!
Test:
var count = 0
for i in lazy(1...1_000_000_000_000).reverse() {
if ++count > 5 {
break
}
println(i)
}
For Swift 2.0 in Xcode 7:
for i in (1...10).reverse() {
print(i)
}
Note that in Swift 2.0, (1...1_000_000_000_000).reverse(...
“ImportError: No module named” when trying to run Python script
...d the folder in which you told the notebook to operate from in your ipython_notebook_config.py file (typically using the c.NotebookManager.notebook_dir setting).
The solution is to provide the python interpreter with the path-to-your-module. The simplest solution is to append that path to your sys....
Explicitly calling return in a function or not
...t return. The following plot is created from data selected this way:
bench_nor2 <- function(x,repeats) { system.time(rep(
# without explicit return
(function(x) vector(length=x,mode="numeric"))(x)
,repeats)) }
bench_ret2 <- function(x,repeats) { system.time(rep(
# with explicit return
(funct...
What is the effect of extern “C” in C++?
...n it posted yet.
You'll very often see code in C headers like so:
#ifdef __cplusplus
extern "C" {
#endif
// all of your legacy C code here
#ifdef __cplusplus
}
#endif
What this accomplishes is that it allows you to use that C header file with your C++ code, because the macro "__cplusplus" will...
Decorators with parameters?
I have a problem with the transfer of variable 'insurance_mode' by the decorator. I would do it by the following decorator statement:
...