Python_utils.txt

1) List
  lst1 + lst2
  cmp(list1, list2)
	sorted(lst)
	lst.sort()
	lst.append(e)
	lst.pop([i]) # i is optional; cannot pop from an empty list
	lst.extend(L) # equals to a[len(a):] = L
	lst.insert(i,e) # check what the result is when abs(i) > e
	lst.index(e) # find the first appearance of e
	lst.count(e)
	lst.remove(e) # remove the first appearance of e
	del lst[i]
	del lst[i:j]
	del lst[:]
2) String
	# See: https://docs.python.org/2/library/stdtypes.html#string-methods
	print r'C:\some\name' # use raw string
	print 'hi\
	yourself'
	a = 'Py' 'thon'
	s='a' s[1:] # out of range slice indexes are handled gracefully
	''.join(['h','i'])
	''.join(str(x) for x in lst)
	'1 2'.split() # default to split on space
	'abc'[::-1] # reverse a string
	'abcde'[3:0:-1] # 'dcb', s[start:end:step]
	list('abc')
	for c1, c2 in zip(s1,s2)
	from string import printable
	s.encode('hex')
	"%x" % 123
3) 
4) if __name__ == '__main__':
5) bitwise operators: x<<y, x>>y, x&y, x|y, ~x, x^y
6) for i in range(len(lst)-1,-1,-1):
7) {char:[] for char in Set}
8) min(lst, key=foo); min(string_1, string2, len)
9) min(result_l,result_r,key=lambda x:x[0])
10) lst = [[k,v] for k,v in dic.items()]
11) lst = filter(lambda item: item != '', lst)
12) lst = map(lambda x:int(x),lst)
    value = reduce(lambda x, y : x + y, [1,2,3])
13) int('5f',16)
14) import re
    pattern = re.compile(r'\s+')
 	  string = re.sub(pattern, '', string)
		re.match(pattern, string)
15) import sys
try:
    txt = open(sys.argv[1],"rt")
    line = txt.readline()
except:
    print "File does not exist!"
    sys.exit()
16) import string
    digs = string.digits + string.letters
17) from collections import deque
	  queue = deque([1,2,3])
	  queue.append(4)
	  queue.popleft() # FIFO
    from collections import Counter
    a=Counter('aabc')
    from collections import defaultdict
    dic = defaultdict(int)
18) integer division: a // b
19) from fractions import Fraction
    a=Fraction(*[1,2])
		a.denominator
		a.numerator
20) eval("x + 3")
21) any(lst)
    all(lst)
22) import unittest