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May 31, 2009 · One rationale for excluding a string.reverse() method is to give python developers incentive to leverage ...
Aug 9, 2015 · Less code is usually faster in Python. Luckily, you don't have to guess: python -mtimeit -s"s='x'*100000" "for x in s[::-1]: pass" 100 loops, best of 3: 1.99 msec per loop python -mtimeit -s"s='x'*100000" "for x in reversed(s): pass" 1000 loops, best of 3: 1.97 msec per loop python -mtimeit -s"s='x'*100000" "for i in xrange(len(s)-1, 0-1, -1): s[i]" 100 loops, best of 3: 4.95 msec per loop
The "-1" part represents the "step" part of the slicing—in this case, it goes through the string 1 character at a time, but backwards (a negative step means start from the end of the string). If you specify the step to be 2, for instance, you would get every other character of the string, starting with the first one.
Literally the first thing? You get the last character of the string, right? So the reverse of a string is the last character, followed by the reverse of everything but the last character, which is where the recursion comes in. The last character of a string can be written as x[-1] while everything but the last character is x[:-1].
Here is a function based on the best, fastest, and most Pythonic answer above and in current Python 3 syntax: def reverse_hex(hex_string): if isinstance(hex_string, str): input_is_string = True hex_string = hex_string.encode() a = array.array('H', hex_string) a.reverse() output = a.tobytes() if input_is_string: return output.decode() else ...
Apr 30, 2016 · I was able to come up with two different ways to reverse a string in Python. Common sense dictates that code with more lines should run slower. I reversed a the string in two ways. Implementation 1: "".join(reversed(map(lambda x:x,st))) Implementation 2: st[::-1] These have similar performance.
Oct 15, 2010 · I find (contrary to some other suggestions) that l.reverse() is by far the fastest way to reverse a long list in Python 3 and 2. I'd be interested to know if others can replicate these timings. I'd be interested to know if others can replicate these timings.
def string_to_list(string): '''function takes actual string and put each word of string in a list''' list_ = [] x = 0 #Here x tracks the starting of word while y look after the end of word. for y in range(len(string)): if string[y]==" ": list_.append(string[x:y]) x = y+1 elif y==len(string)-1: list_.append(string[x:y+1]) return list_ def list_to_reverse(list_): '''Function takes the list of words and reverses that list''' reversed_list = [] for element in list_[::-1]: reversed_list.append ...
Nov 3, 2013 · read() returns the whole file in a single string. That's why when you reverse it, it reverses the lines themselves too, not just their order. You want to reverse only the order of lines, you need to use readlines() to get a list of them (as a first approximation, it is equivalent to s = f.read().split('\n')):
May 19, 2012 · I've been using the following python code to format an integer part ID as a formatted part number string: pn = 'PN-{:0>9}'.format(id) I would like to know if there is a way to use that same format string ( 'PN-{:0>9}' ) in reverse to extract the integer ID from the formatted part number.
