string methods to clean column dataframe
def clean_col(col):
    col = col.strip()
    col = col.replace("(","")
    col = col.replace(")","")
    col = col.lower()
    return col
new_columns = []
for c in df.columns:
    clean_c = clean_col(c)
    new_columns.append(clean_c)
df.columns = new_columns
print(df.columns)