python - 倒着写字

Question

我知道有可能:

sampleword[::-1]

或

reverse(string) 

但我想自己写。我不明白为什么我的代码不起作用。你能帮帮我吗？

h=input('word\n\n');
rev(h)
def rev(h):
    counter=len(h);
    reverse="";
    while counter>0:
        reverse+=h[counter];
        counter=counter-1;
    return reverse
    #print (reverse); ?
input();

Answer 1

你的代码有几个问题，我在这个调整后的脚本的注释中指出了它们:

def rev(h):
    counter=len(h) - 1 # indexes of h go from 0 to len(h) - 1
    reverse=""
    while counter>=0: # changed to >=0
        reverse+=h[counter]
        counter -= 1
    return reverse

h=input('word\n\n');
revers = rev(h) # put rev(h) after the definition of rev!
print(revers) # actually print the result
# deleted your last line

此外，你不需要在 python 中使用 ; 终止行，你可以将 counter=counter-1 写为 counter -= 1.