CSV文件在python中无法保持打开状态

import csv

with open('example.csv', 'r') as file:
    reader = csv.reader(file)
    for row in reader:
        print(row)
# 文件在这里已经被自动关闭

import csv

file = open('example.csv', 'r')
reader = csv.reader(file)
for row in reader:
    print(row)
file.close()  # 手动关闭文件

import csv

try:
    file = open('example.csv', 'r')
    reader = csv.reader(file)
    for row in reader:
        print(row)
finally:
    file.close()  # 确保文件被关闭

import csv
import threading

lock = threading.Lock()

def read_csv():
    with lock:
        with open('example.csv', 'r') as file:
            reader = csv.reader(file)
            for row in reader:
                print(row)

# 创建多个线程
threads = [threading.Thread(target=read_csv) for i in range(5)]
for thread in threads:
    thread.start()
for thread in threads:
    thread.join()