Java: Static transient fields
Nope – you said it yourself, static fields aren’t serialized. Kinda weird that the compiler lets you do that though.
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Django: Make certain fields in a ModelForm required=False
following from comments. Probably yes: class ThatForm(ModelForm): def __init__(self, *args, **kwargs): # first call parent’s constructor super(ThatForm, self).__init__(*args, **kwargs) # there’s a `fields` property now self.fields[‘desired_field_name’].required = False
Mysql Compare two datetime fields
The query you want to show as an example is: SELECT * FROM temp WHERE mydate > ‘2009-06-29 16:00:44′; 04:00:00 is 4AM, so all the results you’re displaying come after that, which is correct. If you want to show everything after 4PM, you need to use the correct (24hr) notation in your query. To make … Read more
IP address storing in MySQL database using PHP [duplicate]
This tutorial might help you. The most efficient way of saving IPv4 addresses is with an INT field (not VARCHAR as you might expect). You convert them using PHP’s ip2long and back using either MySQL’s INET_NTOA function or PHP’s long2ip function. If you need to store IPv6, you’ll want to use a BINARY field instead … Read more
How can I store a lambda expression as a field of a class in C++11?
If you want a class member to be a lambda expression, consider using the std::function<> wrapper type (from the <functional> header), which can hold any callable function. For example: std::function<int()> myFunction = [] { return 0; } myFunction(); // Returns 0; This way, you don’t need to know the type of the lambda expression. You … Read more
Get distinct values of Queryset by field
What you want is: Visit.objects.filter(stuff).values(“ip_address”).annotate(n=models.Count(“pk”)) What this does is get all ip_addresses and then it gets the count of primary keys (aka number of rows) for each ip address.
When have you come upon the halting problem in the field? [closed]
I literally got assigned the halting problem, as in “write a monitor plugin to determine whether a host is permanently down”. Seriously? OK, so I’ll just give it a threshold. “No, because it might come back up afterward.” Much theoretical exposition ensued.
Pandas: join DataFrames on field with different names? [duplicate]
I think what you want is possible using merge. Pass in the keyword arguments for left_on and right_on to tell Pandas which column(s) from each DataFrame to use as keys: pandas.merge(df1, df2, how=’left’, left_on=[‘id_key’], right_on=[‘fk_key’]) The documentation describes this in more detail on this page.
Auto-implemented getters and setters vs. public fields
I tend to agree (that it seems needlessly verbose), although this has been an issue our team hasn’t yet resolved and so our coding standards still insist on verbose properties for all classes. Jeff Atwood dealt with this a few years ago. The most important point he retrospectively noted is that changing from a field … Read more
Get all private fields using reflection
It is possible to obtain all fields with the method getDeclaredFields() of Class. Then you have to check the modifier of each fields to find the private ones: List<Field> privateFields = new ArrayList<>(); Field[] allFields = SomeClass.class.getDeclaredFields(); for (Field field : allFields) { if (Modifier.isPrivate(field.getModifiers())) { privateFields.add(field); } } Note that getDeclaredFields() will not return … Read more