concatenate items in dictionary in python using list comprehension

Question

EDIT: Clarified the question a bit

How can I get a string from a dictionary with the format

key1 = value1
key2 = value2

in a relatively fast way ? (relative to plain concatenation)

Answer 1

Like this:

DATA = {'key1': 'value1', 'key2': 'value2'}
print "\n".join(sorted(["%s = %s" % (k,v) for (k,v) in DATA.iteritems()]))

Answer 2

print '\n'.join('%s = %s' % (key, value) for key, value in d.iteritems())

Answer 3

There's no reason to use list comprehension here.

Python 3.x:

for k,v in mydict.items():
  print(k, '=', v)

Python 2.x:

for k,v in mydict.iteritems():
  print k, '=', v

EDIT because of comment by OP in another answer:

If you're passing it to a function and not printing it here, then you should just pass the generator to the function, or the dict itself and let the function handle whatever it needs to do with it.

This is much better than converting it to a string inside a namespace where it's not even needed. The function should do that, since that's where it's used.

I made a wrapper function, since editing the main function is out of the question.

def log_wrap(mydict):
    mystr = '\n'.join(['%s = %s' % (k,v) for k,v in mydict.iteritems()])
    write_to_log(mydict)

log_wrap(mydict)

Answer 4

Explicit is better than implicit: list comprehension is a way to create list, not to avoid loops.
From PEP 202:

List comprehensions provide a more concise way to create lists in situations where map() and filter() and/or nested loops would currently be used.

What is the usefulness to create such kind of code in python?
It is more compact, and so? Given that code is read much more times than it is written, what is the advantage in it?
Tor Valamo's solution, although not what asked in original request, is in my opinion far more readable, and therefore to prefer.

EDIT after question update
Join is a good way to implement a fast concatenation from a list - and replies from Nadia and Ritchie are good examples of how to use it.
Again, I would not perform everything in a single line, but I would split it in various steps to empathize readability.

Answer 5

I prefer the pythonic way:

mydict = {'a':1, 'b':2, 'c':3}
for (key, value) in mydict.items():
    print key, '=', value