python怎么逆序

>>> arr = [1,2,3,4,3,4]

>>> print (arr[::-1])

[4, 3, 4, 3, 2, 1]

>>> arr = [1,2,3,4,3,4]

>>> arr.reverse()

>>> print (arr)

[4, 3, 4, 3, 2, 1]

arr = [1,2,3,4,3,4]

reversed_arr = []

for i in reversed(arr): 

    reversed_arr.append(i)

print (reversed_arr)

[4, 3, 4, 3, 2, 1]

param = 'hello'

print (param[::-1])

olleh

param = 'hello'

rev_str = ''

for i in reversed(param):   

    rev_str += i

print (rev_str)

olleh

param = 'hello'

rev_arr = []

for i in reversed(param): 

    rev_arr.append(i)

print (''.join(rev_arr))

olleh

sorted(iterable, cmp=None, key=None, reverse=False) --> new sorted list

param = 'hello' #返回元素内的排序

rev_str = ''.join(sorted(param)) #sorted(param)返回倒序排列的数组

['e', 'h', 'l', 'l', 'o']

print rev_str

'ehllo'