In Python, is it better to use list comprehensions or for-each loops?

Question

Which of the following is better to use and why?

Method 1:

for k, v in os.environ.items():
       print \"%s=%s\" % (k, v)

Method 2

Answer 1

I agree with @Ben, @Tim, @Steven:

• readability is the most important thing (do "import this" to remind yourself of what is)
• a listcomp may or may not be much faster than an iterative-loop version... it depends on the total number of function calls that are made
• if you do decide to go with listcomps with large datasets, it's better to use generator expressions instead

Example:

print "\n".join("%s=%s" % (k, v) for k,v in os.environ.iteritems())

in the code snippet above, I made two changes... I replaced the listcomp with a genexp, and I changed the method call to iteritems(). [this trend is moving forward as in Python 3, iteritems() replaces and is renamed to items().]