大约有 42,000 项符合查询结果（耗时：0.0442秒） [XML]
differentiate null=True, blank=True in django
...o need your database to allow NULL values for that field. The exception is CharFields and TextFields, which in Django are never saved as NULL. Blank values are stored in the DB as an empty string ('').
A few examples:
models.DateTimeField(blank=True) # raises IntegrityError if blank
models.DateTi...
Error handling in C code
...rs into something human readable. Can be simple. Just error-enum in, const char* out.
I know this idea makes multithreaded use a bit difficult, but it would be nice if application programmer can set an global error-callback. That way they will be able to put a breakpoint into the callback during bug...
Why do we need argc while there is always a null at the end of argv?
...
...Which is a shame, in a way. If we had int main(char *argv[], int argc, ...), then some programs could just omit the argc because they do not need it. Opposite (needing argc but not argv) is probably never useful in a real program.
– hyde
...
What's best SQL datatype for storing JSON string?
...d as of SQL Server 2005 and should not be used for new development. Use VARCHAR(MAX) or NVARCHAR(MAX) instead
IMAGE, VARBINARY(MAX) : IMAGE is deprecated just like TEXT/NTEXT, and there's really no point in storing a text string into a binary column....
So that basically leaves VARCHAR(x) or NVARC...
Linux: compute a single hash for a given folder & contents?
...
@RichardBronosky - Let us assume we have two files, A and B. A contains "foo" and B contains "bar was here". With your method, we would not be able to separate that from two files C and D, where C contains "foobar" and D contain...
How to un-escape a backslash-escaped string?
...WARNING: value.encode('utf-8').decode('unicode_escape') corrupts non-ASCII characters in the string. Unless the input is guaranteed to only contain ASCII characters, this is not a valid solution.
– Alex Peters
Jun 9 '19 at 11:46
...
Is this a “good enough” random algorithm; why isn't it used if it's faster?
... |12000%n", name);
for (int i = 0; i < 10; i++) {
char[] bar = " ".toCharArray(); // 50 chars.
Arrays.fill(bar, 0, Math.max(0, Math.min(50, frequencies[i] / 100 - 80)), '#');
System.out.printf("0.%dxxx:...
extract part of a string using bash/cut/split
...gs based on position using numbers:
${MYVAR:3} # Remove the first three chars (leaving 4..end)
${MYVAR::3} # Return the first three characters
${MYVAR:3:5} # The next five characters after removing the first 3 (chars 4-9)
You can also replace particular strings or patterns using:
${MYVAR/sear...
Should I use static_cast or reinterpret_cast when casting a void* to whatever
...g between pointer types (as is fairly common when indexing in memory via a char*, for example), static_cast will generate a compiler error and you'll be forced to use reinterpret_cast anyway.
In practice I use reinterpret_cast because it's more descriptive of the intent of the cast operation. You c...
How to reuse an ostringstream?
...ct of the deprecated std::strstream, which was able to write directly to a char array you allocated on the stack. You had to insert a terminating null manually. However, std::ends is not deprecated, i think because it's still useful as in the above cases.
...