Reverse a string in Python

@Paolo's s[::-1] is fastest; a slower approach (maybe more readable, but that's debatable) is ''.join(reversed(s)).

Attempting a canonical answer for this question:

"There is no built in reverse function in Python's str object. What is the best way of implementing this?"

While ''.join(reversed('foo')) is readable, it requires calling a string method, str.join, on another called function, which can be rather slow

Much faster is using a reverse slice:

'foo'[::-1]

But how can we make this more readable and understandable to someone less familiar with the intent of the original author? Let's create a named slice object, and pass it to the subscript notation.

start = stop = None
step = -1
reverse_slice = slice(start, stop, step)
'foo'[reverse_slice]

Implement as Function

To actually implement this as a function, I think it is semantically clear enough to simply use a descriptive name:

def reverse_string(a_string):
    return a_string[::-1]

And usage is simply:

reverse_string('foo')

Demo of timings (differences are probably exacerbated by the shortness of the string being reversed):

>>> min(timeit.repeat("''.join(reversed('foo'))"))
2.2613844704083021
>>> min(timeit.repeat("'foo'[::-1]"))
0.28049658041891234
>>> min(timeit.repeat("start=stop=None; step=-1; 'foo'[start:stop:step]"))
0.37622163503510819
>>> min(timeit.repeat("start=stop=None; step=-1; reverse_slice = slice(start, stop, step); 'foo'[reverse_slice]"))
0.54768217598029878

And for the function:

>>> def reverse_string(a_string):
...     return a_string[::-1]
...     
>>> min(timeit.repeat("reverse_string('foo')", 'from __main__ import reverse_string'))
0.47710669976368081

name="mohit"
rev_name=''
for i in range(len(name)-1,-1,-1):
   rev_name+=name[i]


print rev_name

def reverse(st):
    rev = ""
    for i in range(0 ,len(st)):
        rev += st[(len(st) -1) - i]
    return rev

Reverse a string in python without using reversed() or [::-1]

def reverse(test):
    n = len(test)
    x=""
    for i in range(n-1,-1,-1):
        x += test[i]
    return x