After saving, all sheets in the Excel file are deleted except for the one to which I wrote new data, how to fix it?
def teach_add_3():
with pd.ExcelWriter('bd1.xlsx', engine='openpyxl', mode='a') as writer:
df.to_excel(writer, sheet_name='teachers')
teacher = input("Enter teacher: ")
subject = input("Enter subject: ")
df.loc[index, 'Преподаватели'] = teacher
df.loc[index, 'Предметы'] = subject
df.to_excel(writer, sheet_name='teachers')