Python enumerate() 函数如何实现索引功能

1.描述：

enumerate()函数用于将一个可遍历的数据对象(如列表，元组，字符串)组合为一个索引序列，同时列出数据和数据索引(下标)，一般用于for循环当中

2.语法

enumerate(sequence, [start=0])

3.参数：

• sequence：一个序列，迭代器或其他支持迭代对象
• start：可选参数，下标起始位置，默认从索引0开始

4.返回值

返回enumerate(枚举)对象

5.实例

list1 = [10,20,30,40,"maple","yf",60]

tup1 = (100,200,300,400,"hao","qazert",600)

str1 = "1234qwertjdsa22323"

for index1,item1 in enumerate(list1):
  print("index1 = %d, item1 = %s" %(index1,item1,))

print("------------------------------")
for index2, item2 in enumerate(list1,start = 2):
  print("index2 = %d, item2 = %s" %(index2,item2,))

print("******************************")
for index3,item3 in enumerate(tup1):
  print("index3 = %d, item3 = %s" % (index3, item3,))

print("==============================")
for index4,item4 in enumerate(tup1, start = 4):
  print("index4 = %d, item4 = %s" % (index4, item4,))

print("%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%")
for index5,item5 in enumerate(str1):
  print("index4 = %d, item4 = %s" % (index5, item5,))

print("$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$")
for index6,item6 in enumerate(str1,start = 6):
  print("index4 = %d, item4 = %s" % (index6, item6,))

#输出的结果如下：
index1 = 0, item1 = 10
index1 = 1, item1 = 20
index1 = 2, item1 = 30
index1 = 3, item1 = 40
index1 = 4, item1 = maple
index1 = 5, item1 = yf
index1 = 6, item1 = 60
------------------------------
index2 = 2, item2 = 10
index2 = 3, item2 = 20
index2 = 4, item2 = 30
index2 = 5, item2 = 40
index2 = 6, item2 = maple
index2 = 7, item2 = yf
index2 = 8, item2 = 60
******************************
index3 = 0, item3 = 100
index3 = 1, item3 = 200
index3 = 2, item3 = 300
index3 = 3, item3 = 400
index3 = 4, item3 = hao
index3 = 5, item3 = qazert
index3 = 6, item3 = 600
==============================
index4 = 4, item4 = 100
index4 = 5, item4 = 200
index4 = 6, item4 = 300
index4 = 7, item4 = 400
index4 = 8, item4 = hao
index4 = 9, item4 = qazert
index4 = 10, item4 = 600
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
index4 = 0, item4 = 1
index4 = 1, item4 = 2
index4 = 2, item4 = 3
index4 = 3, item4 = 4
index4 = 4, item4 = q
index4 = 5, item4 = w
index4 = 6, item4 = e
index4 = 7, item4 = r
index4 = 8, item4 = t
index4 = 9, item4 = j
index4 = 10, item4 = d
index4 = 11, item4 = s
index4 = 12, item4 = a
index4 = 13, item4 = 2
index4 = 14, item4 = 2
index4 = 15, item4 = 3
index4 = 16, item4 = 2
index4 = 17, item4 = 3
$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
index4 = 6, item4 = 1
index4 = 7, item4 = 2
index4 = 8, item4 = 3
index4 = 9, item4 = 4
index4 = 10, item4 = q
index4 = 11, item4 = w
index4 = 12, item4 = e
index4 = 13, item4 = r
index4 = 14, item4 = t
index4 = 15, item4 = j
index4 = 16, item4 = d
index4 = 17, item4 = s
index4 = 18, item4 = a
index4 = 19, item4 = 2
index4 = 20, item4 = 2
index4 = 21, item4 = 3
index4 = 22, item4 = 2
index4 = 23, item4 = 3

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