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GeezerVison is showing github.com — python_test/test3.py at master · jacquen/python_test Expand file tree/ Copy pathtest3.pyMore file actions 62 lines (51 loc) · 1.35 KB / Copy pathtest3.pyFile metadata and controls62 lines (51 loc) · 1.35 KB 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 # 练习列表的切片 # 切片是产生一个新的列表，不会修改原来的列表 l = ['john','miss','mike','jack','amy'] # 获取前三位元素,切片一样包头不包尾 print(l[0:3]) # 获取后三位元素 print(l[2:]) # 支持负数的哈，往后数第一个为-1 print(l[-3:]) # 完全复制一个列表 print(l[:]) # 按步长来取元素,步长为2 print(l[::2]) # tuple也可以切片操作 t=(1,2,3,4,5,78,9,10) print(t[::3]) # 而字符串也支持切片操作，因为他也是一个序列 s = 'sergiojune' print(s[-4:]) # 作业：利用切片操作，实现一个trim()函数，去除字符串首尾的空格 def trim(str): n1 = 0 n2 = len(str)-1 for num in range(len(str)): if str[num] == ' ': continue else: n1 = num break for num in range(n1,len(str),-1): if str[num] == ' ': continue else: n2 = num break return str[n1:n2+1] # 上述方法较复杂，参考了别人的写法，重新写 def trim2(str): while True: if str[0] == ' ': str = str[1:] else: break while True: if str[-1] == ' ': str = str[0:-1] else: break return str s = ' hello world ' print(trim2(s)) |
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