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How do I filter ForeignKey choices in a Django ModelForm?
...e fields named directly.
form.rate.queryset = Rate.objects.filter(company_id=the_company.id)
If you take the default ModelForm object, form.fields["rate"].queryset = ...
This is done explicitly in the view. No hacking around.
...
Asking the user for input until they give a valid response
...rsed.
while True:
try:
# Note: Python 2.x users should use raw_input, the equivalent of 3.x's input
age = int(input("Please enter your age: "))
except ValueError:
print("Sorry, I didn't understand that.")
#better try again... Return to the start of the loop
...
Are there legitimate uses for JavaScript's “with” statement?
... same technique used elsewhere - the Chromium source code!
InjectedScript._evaluateOn = function(evalFunction, object, expression) {
InjectedScript._ensureCommandLineAPIInstalled();
// Surround the expression in with statements to inject our command line API so that
// the window object...
What is the function __construct used for?
I have been noticing __construct a lot with classes. I did a little reading and surfing the web, but I couldn't find an explanation I could understand. I am just beginning with OOP.
...
Extract traceback info from an exception object
...n you're using.
In Python 3
It's simple: exceptions come equipped with a __traceback__ attribute that contains the traceback. This attribute is also writable, and can be conveniently set using the with_traceback method of exceptions:
raise Exception("foo occurred").with_traceback(tracebackobj)
...
BaseException.message deprecated in Python 2.6
...s that only a
single string argument be passed to the constructor."""
__str__ and __repr__ are already implemented in a meaningful way,
especially for the case of only one arg (that can be used as message).
You do not need to repeat __str__ or __init__ implementation or create _get_message as s...
How can I use “sizeof” in a preprocessor macro?
....
Following snippets will produce no code if sizeof(someThing) equals PAGE_SIZE; otherwise they will produce a compile-time error.
1. C11 way
Starting with C11 you can use static_assert (requires #include <assert.h>).
Usage:
static_assert(sizeof(someThing) == PAGE_SIZE, "Data structure do...
Chaining multiple filter() in Django, is this a bug?
...el):
blog = models.ForeignKey(Blog)
headline = models.CharField(max_length=255)
pub_date = models.DateField()
...
objects
Assuming there are some blog and entry objects here.
queries
Blog.objects.filter(entry__headline_contains='Lennon',
entry__pub_date__year=2008)
Blog.object...
Ora-00257 错误处理一列 - 数据库(内核) - 清泛网 - 专注C/C++及内核技术
...列sqlplus assysdba报错ORA-12162切回系统确认系统当前的ORACLE_HOME和ORACLE_SID环境变量[oracle@asdlabdb01~]$echo$ORACLE_HOME空的[oracle...sqlplus /as sysdba
报错ORA-12162
切回系统
确认系统当前的ORACLE_HOME和ORACLE_SID环境变量
[oracle@asdlabdb01 ~]$ echo $ORA...
单页web应用（SPA）的简单介绍 - 更多技术 - 清泛网 - 专注C/C++及内核技术
... main.innerHTML=data;
}
});
}
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参考原文链接：http://www.cnblogs.com/constantince/p/5586851.html
单页应用 SPA