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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
...
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.
...
Extracting text from HTML file using Python
..."style"]):
script.extract() # rip it out
# get text
text = soup.get_text()
# break into lines and remove leading and trailing space on each
lines = (line.strip() for line in text.splitlines())
# break multi-headlines into a line each
chunks = (phrase.strip() for line in lines for phrase in ...
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...
What does “#define _GNU_SOURCE” imply?
...
Defining _GNU_SOURCE has nothing to do with license and everything to do with writing (non-)portable code. If you define _GNU_SOURCE, you will get:
access to lots of nonstandard GNU/Linux extension functions
access to traditional fu...