StringIO

from io import StringIO

#像文件一样写入
f = StringIO()
f.write("some words")
f.write("other words")
print(f.getvalue())  # some wordsother words
f.close()

# 初始化，然后，像读文件一样读取
f1 = StringIO("code")
print(f1.read())  # code
f1.close()

BytesIO

from io import BytesIO

fb = BytesIO()
fb.write("中国".encode("utf-8"))
fb.write("美丽".encode("utf-8"))
print(fb.getvalue().decode("utf-8"))
# 中国美丽
fb.close()

# 像读文件一样读取
fb1 = BytesIO("中国".encode("utf-8"))
print(fb1.read())
# b'\xe4\xb8\xad\xe5\x9b\xbd'
fb1.close()