I have a data frame (df_bv_tikkie): Omschrijving IBAN_Tik /TRTP/iDEAL/IBAN//BIC/ABNANL2A/NAME/name via Tikkie/REMI/00345346356 3253636 Tikkie NL30ABNA9999999991/EREF/11-07-2024 03:32 0031039140883718 None SEPA Overboeking IBAN: BIC: NL30ABNA9999999992 Naam: AAB RETAIL INZ TIKKIE Omschrijving: Tikkie ID 390853985 1771 None I am trying to extract the IBAN grom the 'Omschrijving' column and to write it into the 'IBAN_Tik' column. The desired result is: Omschrijving IBAN_Tik /TRTP/iDEAL/IBAN//BIC/ABNANL2A/NAME/name via Tikkie/REMI/00345346356 3253636 Tikkie NL30ABNA9999999991/EREF/11-07-2024 03:32 0031039140883718 NL30ABNA9999999991 SEPA Overboeking IBAN: BIC: NL30ABNA9999999992 Naam: AAB RETAIL INZ TIKKIE Omschrijving: Tikkie ID 390853985 1771 NL30ABNA9999999992 I have first tried: import re pattern = r'^NL[0-9]{2}[A-z0-9]{4}[0-9]{10}$' df_bv_tikkie = df_bv_tikkie.reset_index() index_Omschrijving = df_bv_tikkie.columns.get_loc('Omschrijving') df_bv_tikkie['IBAN_Tik'] = None index_iban = df_bv_tikkie.columns.get_loc('IBAN_Tik') for row in range(0, len(df_bv_tikkie)): iban = re.search(pattern, df_bv_tikkie.iat[row, index_Omschrijving]) print(iban) df_bv_tikkie.iat[row, index_iban] = iban This resulted only in None values in 'IBAN_Tik' Then I tried df_bv_tikkie['Omschrijving'].str.contains(pattern) This also results in None values, as if the pattern is not recognised However if I apply the pattern to a series import re pattern = r'^NL[0-9]{2}[A-z0-9]{4}[0-9]{10}$' testiban2 = ['/TRTP/iDEAL/IBAN//BIC/ABNANL2A/NAME/name via Tikkie/REMI/00345346356 3253636 Tikkie NL30ABNA9999999991/EREF/11-07-2024 03:32 0031039140883718', 'SEPA Overboeking IBAN: BIC: NL30ABNA9999999992 Naam: AAB RETAIL INZ TIKKIE Omschrijving: Tikkie ID 390853985 1771'] for x in testiban: result = re.search(pattern, x) if result: print(x) this will print NL30ABNA9999999991 NL30ABNA9999999992 --> suggesting that the pattern is accurate so I don understand why my first two attempts do not recognise the pattern and or don print it to the column Continue reading...