Updating Change_Column_Value: TypeError Issue

Hi - I am kinda new to GraphQL and I am trying to write a code that will update a column in my board with data from a .csv file saved to my drive. I tried running the code but get this error message:
TypeError: not all arguments converted during string formatting

Code:
for index, row in dataframe.iterrows():
Availability = str(row[‘Availability’]).replace(“,”, “”)
item_id = str(row[‘ID’])
mutation = ‘’’
mutation {
change_column_value(board_id: 309020018, item_id: 309020024, column_id: “Availability”, value: “"500"”) {
id
}
}
‘’’ % (item_id)
print(mutation)
result = client.execute(mutation)
print (result)

I would love any feedback that can be provided! Thanks!