How to avoid writing request.GET.get() twice in order to print it?

Question

I come from a PHP background and would like to know if there\'s a way to do this in Python.

In PHP you can kill 2 birds with one stone like this:

Instead of

Answer 1

Simply try:

print(request.GET.get('q', ''))

which basically prints nothing if the first argument is not present (see dict.get).

---

Alternative solution would be to use a conditional expression in Python:

<expression1> if <condition> else <expression2>

but you'll end up repeating variable twice, for example:

print(request.GET.get('q') if request.GET.get('q') else '')

---

For variable assignments in loops, check in here.

Answer 2

If get() throws an exception when it's not there, you could do

try:
   q = request.GET.get('q')
   print q
except :
   pass

Answer 3

A variation on Alex's answer:

class DataHolder:
    def __init__(self, value=None, attr_name='value'):
        self._attr_name = attr_name
        self.set(value)
    def __call__(self, value):
        return self.set(value)
    def set(self, value):
        setattr(self, self._attr_name, value)
        return value
    def get(self):
        return getattr(self, self._attr_name)
save_data = DataHolder()

Usage:

if save_data(get_input()):
    print save_data.value

or if you prefer an alternative interface:

if save_data.set(get_input()):
    print save_data.get()

I would find this helpful to test a series of regular expressions in an if-elif-elif-elif etc construct, as in this SO question:

import re

input = u'test bar 123'
save_match = DataHolder(attr_name='match')
if save_match(re.search('foo (\d+)', input)):
    print "Foo"
    print save_match.match.group(1)
elif save_match(re.search('bar (\d+)', input)):
    print "Bar"
    print save_match.match.group(1)
elif save_match(re.search('baz (\d+)', input)):
    print "Baz"
    print save_match.match.group(1)

Answer 4

Probably not exactly what you were thinking, but...

q = request.GET.get('q')
if q:
    print q

this?

Answer 5

q = request.GET.get('q')
if q:
    print q
else:
    # q is None
    ...

There's no way of doing assignment and conditionals in one go...

Answer 6

config_hash = {}
tmp_dir = ([config_hash[x]  for x in ["tmp_dir"] if config_hash.has_key(x)] or ["tmp"])[0]
print tmp_dir
config_hash["tmp_dir"] = "cat"
tmp_dir = ([config_hash[x]  for x in ["tmp_dir"] if config_hash.has_key(x)] or ["tmp"])[0]
print tmp_dir