Since I'm new to Python, I'm using this as a place to jot down tips and neat ways to do things. I doubt anything here will be groundbreaking, but for a newbie, might be of some use. I'm using Python 2.5 - I have no idea if this works for previous versions.

String Concatenation

# rather than this
string s = ""
for x in list:
  s += x

do this
s = "".join(list)
if generating bits sequentially, do this
slist = [some_function(x) for x in list]
s = "".join(slist)

Formatting & Concatenation

# don't do this
html = "" + head + body + footer + ""

# do this
html = "%s %s %s" % (head, body, footer)

# or this using a dictionary
html = "%(head)s %(body)s %(footer)s" % vars()

Finding a string

# nope
bleh = "hi there!"
if bleh.find("hi") > -1:
  # ...

# yep
if "hi" in bleh:
  ...

Lists

Similar to the lambda statement:

numbers = [1,2,3,4,5]
squares = [number*number for number in numbers]
>>> [1,4,9,16,25] 

Filtering:

numbers = [1,2,3,4,5]
under_4 = [number for number in numbers if number < 4]
>>> [1,2,3]

Filter and Map:

numbers = [1,2,3,4,5]
square_under_4 = [number*number for number in numbers if number < 4]
>>> [1,4,9]

Getting the index in a for loop

list = ['a','b','c','d']
for index, chr in enumerate(list):
  ...

See if something's in a list

list = [1,2,3,4]
if 1 in list:
  print '%i is in the list' % 1

Any and All over lists

numbers = [1,2,3,4,5]
if any(number < 4 for number in numbers):
  print 'less than 4: ' + number

if all(number < 10 for number in numbers):
  print 'great success!'

Lambda

squares = map(lambda a: a*a, [1,2,3,4,5])
>>> [1, 4, 9, 16, 25]

Meta Stuff

What methods does str have?

dir(str)

What's the str.find() method all about?

print getattr(str, 'find').__doc__

Dictionaries

# can do this
d = { 'a': 1, 'b': 2, 'c': 3 }

can also do this
d = dict(a=1, b=2, c=3)

Truthiness

has_email = True
name = person.email if has_email else 'Anonymous'

different way, kinda like C ternary statement (a = b ? c : d)
name = has_email and person.email or 'Anonymous'

Other Helpful Links

• GVR: Loop Optimization