如何在 Python 的 for 循环中进行计数

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在 Python 中的 for 循环中计数

How to count in a for loop in Python

使用该enumerate()函数在 for 循环中计数，例如
for index, item in enumerate(my_list):。该函数接受一个可迭代对象并返回一个包含元组的对象，其中第一个元素是索引，第二个元素是项目。

主程序
my_list = ['a', 'b', 'c']

# ✅ count in for loop

for index, item in enumerate(my_list):
    print(index, item)

# 👇️
# 0 a
# 1 b
# 2 c

# ---------------------------------------------

# ✅ count in for loop starting with N

for count, item in enumerate(my_list, start=1):
    print(count, item)

# 👇️
# 1 a
# 2 b
# 3 c

# ----------------------------------------------

# ✅ manually incrementing counter in for loop

counter = 0

for item in my_list:
    counter += 1
    print(counter)

print(counter)  # 👉️ 3

enumerate函数接受一个可迭代对象并返回一个包含元组的
枚举对象，其中第一个元素是索引，第二个元素是项目。

我们可以直接解压索引（或计数）和for循环中的项目。

主程序
my_list = ['a', 'b', 'c']


for index, item in enumerate(my_list):
    print(index, item)

# 👇️
# 0 a
# 1 b
# 2 c

该enumerate函数有一个可选start参数，默认为
0.

If you need to start the count from a different number, e.g. 1, specify the
start argument in the call to enumerate().

main.py
my_list = ['a', 'b', 'c']


for count, item in enumerate(my_list, start=1):
    print(count, item)

# 👇️
# 1 a
# 2 b
# 3 c

The count variable has an initial value of 1 and then gets incremented by
1 on each iteration.

Alternatively, you can manually count in the for loop.

To count in a for loop:

  1. Initialize a count variable and set it a number.
  2. Use a for loop to iterate over a sequence.
  3. On each iteration, reassign the count variable to its current value plus N.
main.py
my_list = ['a', 'b', 'c']


count = 0

for item in my_list:
    count += 1
    print(count)

print(count)  # 👉️ 3

We declared a count variable and initially set it to 0.

On each iteration, we use the += operator to reassign the variable to its current value plus N.

The following 2 lines of code achieve the same result:

  • count += 1
  • count = count + 1

下面是一个使用更长的重新分配语法的示例。

主程序
my_list = ['a', 'b', 'c']


count = 0

for item in my_list:
    count = count + 1
    print(count)

print(count)  # 👉️ 3

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