Merge csv files using python without repeating header

I am trying to do this ,

import glob

interesting_files = glob.glob("/home/tcs/PYTHONMAP/test1/*.csv") 

header_saved = False
with open('/home/tcs/PYTHONMAP/output.csv','wb') as fout:
    for filename in interesting_files:
        with open(filename) as fin:
            header =  next(fin)
            if not header_saved:
                fout.write(header)
                header_saved = True
            for line in fin:
                fout.write(line)

and getting

File "/home/tcs/.config/spyder-py3/temp.py", line 11, in <module>
    fout.write(header)

TypeError: a bytes-like object is required, not 'str'

I don't know much about python please help Also i want to know how to split 1 big csv into multiple csv with same header.