Introduction to Python Programming (015) - Usage of the enumerate() function
Table of contents
1. Syntax of enumerate() function
The function of the enumerate() function is to form a traversable or iterable object into an index sequence according to the set sequence number. The syntax format is as follows:
enumerate(iterable[,start])
说明：
（1）iterable：表示一个序列、迭代器或其他支持迭代的对象。
（2）start：用于设置下标的起始位置，默认为0。
（3）函数返回一个列表（类型为：enumerate），列表由新生成的序号和原有数据组成的元组构成。
For example:
lang = ["java","go","c","vb","c++"]
list1 = enumerate(lang,1)
print("list1的类型：",type(list1))
print(list1)
print(list(list1))
for i in enumerate(lang,1):
print(i)
运行结果为：
===================== RESTART: C:\Python\Python38\First.py =====================
list1的类型： <class 'enumerate'>
<enumerate object at 0x000001E137D1F780>
[(1, 'java'), (2, 'go'), (3, 'c'), (4, 'vb'), (5, 'c++')]
(1, 'java')
(2, 'go')
(3, 'c')
(4, 'vb')
(5, 'c++')
2. Create an index for an iterable object
The enumerate() function can quickly index and number the elements in an iterable object. For example:
stu = ["刘刚","张静静","王芸","张云涛","刘贝贝"]
list1 = enumerate(stu,1)
for item in list1:
print(item)
运行结果为：
===================== RESTART: C:\Python\Python38\First.py =====================
(1, '刘刚')
(2, '张静静')
(3, '王芸')
(4, '张云涛')
(5, '刘贝贝')
You can also use the enumerate() function directly in the sequence:
stu = ["刘刚","张静静","王芸","张云涛","刘贝贝"]
for item in enumerate(stu,1):
print(item)
运行结果为：
===================== RESTART: C:\Python\Python38\First.py =====================
(1, '刘刚')
(2, '张静静')
(3, '王芸')
(4, '张云涛')
(5, '刘贝贝')
Strings can be indexed using the enumerate() function:
str = "张王李赵刘曹关"
for item in enumerate(str,1):
print(item)
运行结果为：
===================== RESTART: C:\Python\Python38\First.py =====================
(1, '张')
(2, '王')
(3, '李')
(4, '赵')
(5, '刘')
(6, '曹')
(7, '关')
3. Convert strings, lists, etc. into dictionaries
1. Convert string to dictionary
str = "张王李赵刘曹关"
name = dict(enumerate(str,1))
print(name)
运行结果为：
===================== RESTART: C:\Python\Python38\First.py =====================
{
1: '张', 2: '王', 3: '李', 4: '赵', 5: '刘', 6: '曹', 7: '关'}
2. Convert the list into a dictionary and use the serial number as the key of the dictionary
str = ["马芸","马花疼","黄征","丁蕾","许志军","张三疯"]
name = dict(enumerate(str,1))
print(name)
运行结果为：
===================== RESTART: C:\Python\Python38\First.py =====================
{
1: '马芸', 2: '马花疼', 3: '黄征', 4: '丁蕾', 5: '许志军', 6: '张三疯'}
3. Convert the list into a dictionary and use the serial number as the value of the dictionary
str = ["马芸","马花疼","黄征","丁蕾","许志军","张三疯"]
name = dict((item,i) for i,item in enumerate(str,1))
print(name)
运行结果为：
===================== RESTART: C:\Python\Python38\First.py =====================
{
'马芸': 1, '马花疼': 2, '黄征': 3, '丁蕾': 4, '许志军': 5, '张三疯': 6}
4. Create indexes for dictionary keys
Use the enumerate() function to index the keys of the dictionary and generate a tuple consisting of the serial number and the key of the dictionary. For example:
dict = {
"马芸":20,"马花疼":85,"黄征":76,"丁蕾":88,"许志军":102,"张三疯":56}
for item in enumerate(dict,1):
print(item)
for i,item in enumerate(dict,1):
print(i,":",item,end=" ")
运行结果为：
===================== RESTART: C:\Python\Python38\First.py =====================
(1, '马芸')
(2, '马花疼')
(3, '黄征')
(4, '丁蕾')
(5, '许志军')
(6, '张三疯')
1 : 马芸 2 : 马花疼 3 : 黄征 4 : 丁蕾 5 : 许志军 6 : 张三疯