import pandas as pd
from pandas import ExcelWriter
import os

d1 = "asset\path1"
d2 = "asset\path2"

output_dir = "asset\path3"

for fname in os.listdir(d1):
    sheets = []
    i = 0
    while i<10:
        try:
            sheets.append(pd.read_excel(os.path.join(d1, fname),sheet_name=i,encoding='sys.getfilesystemencoding()'))
        except IndexError:
            break
        except Exception as e:
            raise e
        i+=1
    sheets.append(pd.read_excel(os.path.join(d2, fname),sheet_name=0,encoding='sys.getfilesystemencoding()'))

    with ExcelWriter(os.path.join(output_dir,fname)) as writer:
        for n, df in enumerate(sheets):
            df.to_excel(writer,'sheet%s' % n, index = False, header=False)
        writer.save()