codecs

import base64 
import codecs
f = open('j:\pic_png.txt','r')
data = f.read()
head = codecs.decode('89504e470d0a1a0a', 'hex_codec')#16转成bytes类型写入文件中，自动两位两位
#a = bytes.fromhex('89504e470d0a1a0a')
data1 = base64.b64decode(data.encode('ascii'))
f.close()
f = open('j:\\key1.docx','wb+')
f.write(head)
f.write(data1)

f.close()