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How to import multiple .csv files at once?
...olutions in other answers using things like do.call(rbind,...), dplyr::bind_rows() or data.table::rbindlist().
If you really want each data frame in a separate object, even though that's often inadvisable, you could do the following with assign:
temp = list.files(pattern="*.csv")
for (i in 1:lengt...
Counting array elements in Python [duplicate]
... out as 2, as does len(array([[0, 0], [0, 0]])).
– EL_DON
Jan 19 '18 at 22:49
how about index of array? for example, w...
What is the __DynamicallyInvokable attribute for?
...q.Enumerable in DotPeek I notice that some methods are flavoured with a [__DynamicallyInvokable] attribute.
2 Answers
...
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)
share
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...
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
...
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...
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(...
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...