Reading Notes III:Think Python

字符串取数

a[0]：取出第一位
a[-1]：取出最后一位
a[1:-1]: 取出除开头核结尾的位
a[::-1]：字段倒叙输出

回文判断

def first(word):
    """Returns the first character of a string."""
    return word[0]
def last(word):
    """Returns the last of a string."""
    return word[-1]
def middle(word):
    """Returns all but the first and last characters of a string."""
    return word[1:-1]
def is_palindrome(word):
    """Returns True if word is a palindrome."""
    if len(word) <= 1:
        return True
    if first(word) != last(word):
        return False
    return is_palindrome(middle(word))

常用函数

fruit='banana'
fruit.count('a')  #统计字母个数，输出结果：3
fruit.capitalize() #首字母大写，输出结果：Banana
fruit.[0:5:2] #返回特定位置上的数，输出结果：bnn
fruit.center(20,'*') #使字段居中，输出结果：'*******banana*******'
fruit.endswith("a") #判断最后一位，返回True
fruit.endswith("n") #返回False
fruit.rfind("na") #返回最大位包含字符串的，返回4
fruit.lstrip() #去掉左边的空格

Chapter 8 Exercise 8.5.

def rotate_word(alpha,num):   
    new=''
    for a in range(0,len(alpha)):
        if a<=len(alpha)-1:
            new=new+chr(ord(alpha[a])+num)
            a+=1
    return new #输出示例：rotate_word("AB",2):CD