Python中enumerate函数详解之遍历中的索引神器

fruits = ['apple', 'banana', 'cherry']
for index, fruit in enumerate(fruits):
  print(f"索引 {index} 对应的水果是 {fruit}")
# 输出：
# 索引 0 对应的水果是 apple
# 索引 1 对应的水果是 banana
# 索引 2 对应的水果是 cherry

students = ['Alice', 'Bob', 'Charlie']
for rank, student in enumerate(students, start = 1):
  print(f"排名第 {rank} 的学生是 {student}")
# 输出：
# 排名第 1 的学生是 Alice
# 排名第 2 的学生是 Bob
# 排名第 3 的学生是 Charlie

scores = [85, 90, 78, 95]
for index, score in enumerate(scores):
  if index == 2:
    scores[index] = 80 # 将索引为2的成绩修改为80
print(scores)
# 输出：[85, 90, 80, 95]

colors = ['red', 'blue', 'green', 'blue', 'yellow']
blue_positions = [index for index, color in enumerate(colors) if color == 'blue']
print(blue_positions)
# 输出：[1, 3]

with open('example.txt', 'r', encoding='utf-8') as file:
for line_number, line in enumerate(file, start = 1):
  print(f"第 {line_number} 行: {line.strip()}")

number = 123
# 错误示范，会抛出 TypeError: 'int' object is not iterable
for index, value in enumerate(number):
   pass

words = ['hello', 'world']
# 错误示范，会导致变量赋值错误
for word, index in enumerate(words):
  pass

# 假设要统计学生考试排名，从1开始更合理
ranks = [1, 2, 3]
# 错误示范，起始索引设为0不符合排名习惯
for rank, student in enumerate(ranks, start = 0):
  print(f"排名第 {rank} 的学生成绩是 {student}")

names = ['Alice', 'Bob', 'Charlie']
ages = [25, 30, 35]
for index, (name, age) in enumerate(zip(names, ages), start = 1):
  print(f"序号 {index}，姓名 {name}，年龄 {age}")
# 输出：
# 序号 1，姓名 Alice，年龄 25
# 序号 2，姓名 Bob，年龄 30
# 序号 3，姓名 Charlie，年龄 35

nums = [1, 2, 3, 4, 5]
result = list(map(lambda x: x[0] * x[1], enumerate(nums)))
print(result)
# 输出：[0, 2, 6, 12, 20]

my_list = ['a', 'b', 'c']
index = 0
while index < len(my_list):
  value = my_list[index]
  print(f"索引 {index} 处的值是 {value}")
  index += 1