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“刘心向学（47）：enumerate —— 优雅地遍历索引与元素”
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Increase knowledge, leave a beautiful!
Dear, this is LearningYard Academy.
Today, the editor brings you an article.
“Liu Xin Xiang Xue (47): enumerate — Iterate with Index and Value, the pythonic Way
Have you written code like this?”
Welcome to your visit.
在编程中，我们经常需要“一边遍历，一边知道位置”。
传统方式：
In programming, we often need to “loop over items and know their position.”
The traditional way:
for i in range(len(data)):print(i, data[i])
问题：
Problems:
冗长
Verbose
易出错（如索引越界）
Error-prone (e.g., index out of bounds)
可读性差
Harder to read
而 enumerate 的出现，正是为了解决这个问题：
enumerate was designed to solve this:
for i, item in enumerate(items):
print (i, item)
简洁、清晰、安全。
Clean. Clear. Safe.
三、基本语法（Basic Syntax）enumerate (iterable, start=0)iterable
：可迭代对象（列表、元组、字符串等）
iterable
: any iterable (list, tuple, string, etc.)start
：起始索引，默认为 0
返回一个 enumerate 对象，它是一个迭代器，生成 (index, value) 元组。
Returns an enumerate object — an iterator that yields (index, value) tuples.
items = ['a', 'b', 'c']
enum = enumerate(items)print(list(enum)) # [(0, 'a'), (1, 'b'), (2, 'c')]for index, value in enumerate (items):
fruits = ['apple', 'banana', 'cherry']
for i, fruit inenumerate(fruits, start=1):print(f"{i}. {fruit}")# 输出：# 1. apple# 2. banana# 3. cherrywords = ["hello", "world", "python"]
for i, word inenumerate(words):if"o"in word:print(f"Found 'o' at index {i}: {word}")items = ['foo', 'bar', 'baz']
index_map = {item: i for i, item inenumerate(items)}print(index_map) # {'foo': 0, 'bar': 1, 'baz': 2}data = [10, 20, 30]
result = [f"{i}:{x}"for i, x inenumerate(data)]print(result) # ['0:10', '1:20', '2:30']b = ['x', 'y', 'z']for i, x inenumerate(a):for j, y inenumerate(b):if i == j:print(x, y) # 可读性差正确：使用 zipfor
或带索引的 zip：
Or with index:
for i, (x, y) in enumerate(zip(a, b)):
for i, Line in enumerate(log_lines, start=1):
print(f"[Line {i}] {line}")
非常适合日志、文件行号等场景。
Perfect for logs, file lines, etc.
Combined with zip
names = ['Alice', 'Bob']
ages = [25, 30]
fori, (name, age) inenumerate(zip(names, ages), 1):
print(f"{i}. {name}is {age}years old")
enum = enumerate(['a', 'b'])
print(list(enum)) # [(0, 'a'), (1, 'b')]print(list(enum)) # —— 已耗尽！如需多次使用，转换为列表：
If you need to reuse it, convert to list:
enum_list = list(enumerate(items))
仅需元素：直接 for item in items
Only need values: use for item in items
仅需索引：for i in range(n)
Only need indices: use for i in range(n)
需要复杂索引逻辑：仍可用 range(len)
Complex indexing logic: range(len) may still apply
但 绝大多数“索引+元素”场景，enumerate 都是首选。
But for most "index + value" cases, enumerate is the best choice.
enumerate 是 Python 中“小而美”的典范。
enumerate
is a small but beautiful feature in Python.
它不复杂，却极大提升了代码的可读性与安全性。
It’s simple, yet greatly improves code readability and safety.
它提醒我们：
It reminds us:
“不要自己造轮子，善用内置工具。”
“Don’t reinvent the wheel — use built-in tools.”
从今天起，当你写下：
From now on, whenever you write:
for i in range(len(data)):
请停下来，问自己：
Pause and ask:
“我是不是该用 enumerate？”
“Should I use enumerate instead?”
大概率，答案是肯定的。
Chances are, the answer is yes.
因为真正的 Pythonic 代码，不是“能运行”，而是“清晰、简洁、优雅”。
Because truly Pythonic code isn’t just “working” — it’s clear, concise, and elegant.
而 enumerate，正是通往这种境界的一小步。
And enumerate is a small step toward that ideal.
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参考资料：通义千问
参考文献：Beazley, D., & Jones, B. K. (2019). Python Cookbook (3rd ed.). O'Reilly Media.
Hettinger, R. (2019). Transforming Code into Beautiful, Idiomatic Python. PyCon US.
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