s = 'abcd'
int('123') # str to int
# long(), float()
str(123) # int to str
ord(s[0]) # char to int
chr(97) # int to char
# unichar(97) # convert to char using unicode ENCODING
list(s) # str to list ['a','b','c','d']
# tuple(s)
hex(11) # int with base 10 to base 16
# oct(11)

a = ['b', 'c', 'd', 'a']
a.sort() # a = ['a', 'b', 'c', 'd'] # sort in place
s = 'cbda'
sorted(s) # ['a', 'b', 'c', 'd']
# sorted(iterable, cmp=None, key=None, reverse=False) --> return a new sorted list
sorted([5, 2, 3, 1, 4], reverse=False) # [1, 2, 3, 4, 5]
L = [('d',2),('a',4),('b',3),('c',2)]
sorted(L, key=lambda x:(x[1],x[0])) # [('c', 2), ('d', 2), ('b', 3), ('a', 4)]
sorted(L, cmp=lambda x,y:cmp(x[1],y[1])) # [('a', 1), ('b', 2), ('c', 3), ('d', 4)]
sorted(L, key=lambda x:x[1])) # [('a', 1), ('b', 2), ('c', 3), ('d', 4)]
# use 'key' will be faster than 'cmp'
# http://www.cnblogs.com/65702708/archive/2010/09/14/1826362.html

#read file
f = open('text', 'r')
for line in f:
	line = line.strip() # remove '\n', ' ' in the begin and end of the line
	# do something with line

a = set([1,2,3])
b = set([2,3,4])
a.intersection(b) # {2,3}