This to me sounds like a reasonably common problem that junior to intermediate developers tend to face at some point: they either don’t know or don’t trust the contracts they are participating in and defensively overcheck for nulls. Additionally, when writing their own code, they tend to rely on returning nulls to indicate something thus … Read more
This should do the work: df = df.dropna(how=’any’,axis=0) It will erase every row (axis=0) that has “any” Null value in it. EXAMPLE: #Recreate random DataFrame with Nan values df = pd.DataFrame(index = pd.date_range(‘2017-01-01’, ‘2017-01-10′, freq=’1d’)) # Average speed in miles per hour df[‘A’] = np.random.randint(low=198, high=205, size=len(df.index)) df[‘B’] = np.random.random(size=len(df.index))*2 #Create dummy NaN value on … Read more
Firstly, a Java double cannot be a Java null, and cannot be compared with null. (The double type is a primitive (non-reference) type and primitive types cannot be null.) I’m therefore assuming the following: The “null” you are trying to detect is a NULL stored in the database that you are querying. You are using … Read more
String s1 = “”; means that the empty String is assigned to s1. In this case, s1.length() is the same as “”.length(), which will yield 0 as expected. String s2 = null; means that (null) or “no value at all” is assigned to s2. So this one, s2.length() is the same as null.length(), which will … Read more
An object of a class cannot be set to NULL; however, you can set a pointer (which contains a memory address of an object) to NULL. Example of what you can’t do which you are asking: Cat c; c = NULL;//Compiling error Example of what you can do: Cat c; //Set p to hold the … Read more
You should add the option onDelete=”SET NULL” in the annotation of your entity Publication like this: class Publication { /** * @ORM\ManyToOne(targetEntity=”Teacher”, inversedBy=”publications”) * @ORM\JoinColumn(name=”teacher_id”, referencedColumnName=”id”, onDelete=”SET NULL”) */ protected $teacher; } This modification is registered in the table declaration itself. Hence, you need a database migration or a schema change for this to take … Read more
where(‘archived IS NOT NULL’, null, false)
Yes, by using COALESCE. SELECT COALESCE(null_column, 0) AS null_column FROM whatever; COALESCE goes through the list of values you give it, and returns the first non-null value.
null and Empty are very different, and I don’t suggest arbitrarily switching between them. But neither has any extra “cost”, since Empty is a single fixed reference (you can use it any number of times). There is no “pollution” on the stack caused by a ldsfld – that concern is…. crazy. Loading a null is … Read more
I am a fan of always including null explicitly as that carries meaning. While omitting a property leaves ambiguity. As long as your protocol with the server is agreed upon any of the above can work, but if you pass nulls from the server I believe that makes your APIs more flexible later. Should also … Read more