def flatten(lst):
    i = 0
    while(i<len(lst)):
        if isinstance(lst[i],list):
            lst.extend(lst[i])
        i += 1
    return [n for n in lst if not isinstance(n,list)]

lst = [1, [2], [[3], 4], 5]
flatten(lst)
# [1, 5, 2, 4, 3]

from itertools import chain
a = [[1, 2], [3, 4], [5, 6]]
chain(*a)
# [1, 2, 3, 4, 5, 6]

from math import ceil   #ceil為向上取整

def chunkByFor(lst, size):
    return [lst[x*size:x*size+size] 
        for x in range(0,ceil(len(lst)/size))]

def chunkByMap(lst, size): 
    return list(
        map(lambda x: lst[x * size:x * size + size],    	
            list(range(0, ceil(len(lst) / size)))))    	

chunk([1,2,3,4,5],2) # [[1,2],[3,4],5]

lst = [[1,2], [3,4], [5,6]]
list(zip(*lst))
#[(1, 3, 5), (2, 4, 6)]

lst =  [1,2,1,2,3,2,1,4,2]
lst.count(1)
# 3   即lst中1出現(xiàn)了3次

x = [-2,-1,0,1,2]
def test(x): return x**2-2*x

max(x,key=test)
# -2

lst = [1,2,3,4,5,2,3,2,1,2,4]
max(set(lst),key=lst.count)	# 2

def isUnique(lst):    	
    return len(lst) == len(set(lst)) 

x = [1,2,3,4,5,5]
y = [1,2,3,4,5]	
isUnique(x)	# False
isUnique(y)	# True

A = [1,2,3]
B = [1,2,4]
list(set(A).difference(B))	# [3]

def funcMinus(A, B, func):	
    B = set(map(func, B))     #剔除func(B)中的重復元素
    return [a for a in A if fn(a) not in B]	

orders = ['first','second','third']
list(enumerate(orders))
# [(0, 'first'), (1, 'second'), (2, 'third')]
list(enumerate(orders,2))
# [(2, 'first'), (3, 'second'), (4, 'third')]

>>> for i,val in enumerate(orders,1):
...   print(i,val)
...
1 first
2 second
3 third

>>> s = "abcde"
>>> s[::-1]
'edcba'
>>> s == s[::-1]
False