python读取文件read()一直读取不进去

# code:utf-8

if __name__ == '__main__':

    f1 = open('d:/englishbook/Tech2.txt', 'a+', encoding='UTF-8')
    with open('d:/englishbook/Tech10.txt', 'a+', encoding='UTF-8') as file1:
        contents = file1.read()
        print(contents)
        f1.write(contents)

Tech2.txt一直显示0kB

经过尝试发现是需要加一句file1.seek(0)，即

# code:utf-8

if __name__ == '__main__':

    f1 = open('d:/englishbook/Tech2.txt', 'a+', encoding='UTF-8')
    with open('d:/englishbook/Tech10.txt', 'a+', encoding='UTF-8') as file1:
        file1.seek(0) 
        contents = file1.read()
        print(contents)
        f1.write(contents)