查找第一次出现并在没有出现时返回 0 然后将新列附加到 csv (python) 的代码

Question

I am trying to extract values inside a column in a csv. Here is my code so far:

```code```
import csv
with open('Cash_Statement_Pier21 accounts 2019c.csv') as csv_file:
csv_reader = csv.reader(csv_file, delimiter=',')
line_count = 0
for row in csv_reader:
    for line in row:
        index = line.find('@')
        if index != -1:
            print(line[index+2:index+7])
        else:
            index = line.find('RATE')
            if index != -1:
                print(line[index +2])

However, this code fails for lines with multiple "@"s and it only prints out the list in python. How would I append this code such that it a) only takes into account the first "@" on every line and b) creates a new column in my csv?

Thanks so much in advance!

EDIT SAMPLE INPUT ( seperated lines for readability) NOVO NORDISK A/S 216757.000 SHS @ 5.15000000 EXDTE-22MAR19 PAYDTE-26MAR19 TAXABLE RECLAIMABLE TAXED AT .270000%

NOVO NORDISK A/S 205395.000 SHS @ 3.00000000 EXDTE-16AUG19 PAYDTE-20AUG19 TAXABLE RECLAIMABLE TAXED AT .270000%

NOVO NORDISK A/S TAX RECLAIM PAID 79000.000 EX-DT:20MAR15 PY-DT:24MAR15 CURRENCY TIP # 1150790014348

PING AN INSURANCE GROUP CO OF HK/02318 1184000.000 SHS @ 1.28414399EXDTE-23MAY19 PAYDTE-28JUN19 TAXABLE AT ISSUE RATE .100000%

BANK CENTRAL ASIA TBK PT    3314200.000 SHS @ 100.00000000 EXDTE-06DEC19 PAYDTE-20DEC19 TAXABLE AT ISSUE RATE .200000%

Answer 1

There are 2 different problems here.

1. How to only process first @ or each line?

   I will assume that despite what you have shown, you are actually processing a true csv file with more than one field per row and only want to process the first field containing a @ caracter. If you do not want to search for RATE if you have found @ , it is trivial: just add a break statement:

    for row in csv_reader: for line in row: index = line.find('@') if index != -1: print(line[index+2:index+7]) break // ignore any other field in that row else: ...

   If you want to process the first @ and the first RATE on each row, you will have to use a boolean to ignore any @ but the first, but still continue up to a RATE :

    for row in csv_reader: first = True for line in row: if first: index = line.find('@') if index != -1: print(line[index+2:index+7]) first = False // ignore any other field in that row else: ...

2. How to add a new field to a CSV?

   A CSV is a text file. The only reliable way to change it is to rewrite everything on a temporary file and when done remove the old file (or rename it as a backup) and rename the temporary to the original name. More or less (only showing high level):

    ok = False with open('Cash_Statement_Pier21 accounts 2019c.csv') as csv_file: with open('Cash_Statement_Pier21 accounts 2019c.tmp', 'w',', newline='') as out_file: csv_reader = csv.reader(csv_file, delimiter=',') csv_writer = csv.writer(out_file, delimiter=') for row in csv_reader: ... row.append(new_column_value) csv_writer.writerow(row) ok = True if ok: // do not rename if an error occured... os.remove('Cash_Statement_Pier21 accounts 2019c.csv') os.rename('Cash_Statement_Pier21 accounts 2019c.tmp', 'Cash_Statement_Pier21 accounts 2019c.csv)'

   We have to wait after the end of the with block to execute the rename, because some OS may refuse to remove or rename an open file.