python open读取文本的三种方式

import time
def main():
    #一次性读取整个文件
    with open('url.txt','r', encoding='utf-8') as f:
        print(f.read())          
    #通过for-in 循环逐行读取 'r' 与mode='r'一样
    with open('url.txt',mode = 'r') as f:
        for line in f:
            print(line, end='')
            time.sleep(1)
    print()
    #读取文件按行读取到列表中
    with open('url.txt') as f:
        lines = f.readlines()
    print (lines)
    
if __name__ == '__main__':
    main()