大约有 48,000 项符合查询结果（耗时：0.0598秒） [XML]
JPA getSingleResult() or null
...pdate method which inserts an Entity when it doesn't exist or update it if it does. To enable this, I have to findByIdAndForeignKey , if it returned null insert if not then update. The problem is how do I check if it exists? So I tried getSingleResult . But it throws an exception if the
...
Get column index from column name in python pandas
...he list of columns to get index for:
[df.columns.get_loc(c) for c in cols if c in df]
share
|
improve this answer
|
follow
|
...
XPath to find elements that does not have an id or class
...
That will give you all tr elements lacking both id and class attributes. If you want all tr elements lacking one of the two, use or instead of and:
//tr[not(@id) or not(@class)]
When attributes and elements are used in this way, if the attribute or element has a value it is treated as if it's t...
select and update database record with a single queryset
...
Just a fair warning... if you use the update method like this then any signals attached to that model or other "code stuff" won't run against the objects. Just a pointer from someone who got burned :)
– DMac the Destroyer
...
How do I unset an element in an array in javascript?
...d, which will then not be reflected correctly in the length of the array.
If you know the key you should use splice i.e.
myArray.splice(key, 1);
For someone in Steven's position you can try something like this:
for (var key in myArray) {
if (key == 'bar') {
myArray.splice(key, 1);
...
Common elements comparison between 2 lists
...der, whereas the list comprehension method preserves the order. Important if anyone needs to consider this. Thanks.
– agftrading
Oct 1 '18 at 15:35
|
...
How to append rows to an R data frame
I have looked around StackOverflow, but I cannot find a solution specific to my problem, which involves appending rows to an R data frame.
...
Python argparse: Make at least one argument required
...
if not (args.process or args.upload):
parser.error('No action requested, add -process or -upload')
share
|
improve thi...
How to efficiently build a tree from a flat structure?
...
Store IDs of the objects in a hash table mapping to the specific object. Enumerate through all the objects and find their parent if it exists and update its parent pointer accordingly.
class MyObject
{ // The actual object
public int ParentID { get; set; }
public int ID { get...
Iterating over each line of ls -l output
...
Set IFS to newline, like this:
IFS='
'
for x in `ls -l $1`; do echo $x; done
Put a sub-shell around it if you don't want to set IFS permanently:
(IFS='
'
for x in `ls -l $1`; do echo $x; done)
Or use while | read instead:
...