Python-最有效的方式来覆盖CSV文件中的特定行

Question

Given the following csv file :

01;blue;brown;black
02;glass;rock;paper
03;pigeon;squirel;shark

My goal is to replace the (unique) line containing '02' in the 1st posisition.

I wrote this piece of code:

with open("csv", 'r+', newline='', encoding='utf-8') as csvfile, open('csvout', 'w', newline='', encoding='utf-8') as out:
    reader = csv.reader(csvfile, delimiter=';')
    writer = csv.writer(out, delimiter=';')
    for row in reader:
        if row[0] != '02':
            writer.writerow(row)
        else:
            writer.writerow(['02', 'A', 'B', 'C'])

But re-writing the whole CSV in an other doesn't seem to be the most efficient way to proceed, especially for large files:

1. Once the match is found, we continue to read till the end.
2. We have to re-write every line one by one.
3. Writing a second file isn't very practical nor is storage efficient.

I wrote a second piece of code who seems to answer to these two problems :

with open("csv", 'r+', newline='', encoding='utf-8') as csvfile:
    content = csvfile.readlines()
    for index, row in enumerate(content):
        row = row.split(';')
        if row[2] == 'rock':
            tochange = index
            break
    content.pop(tochange)
    content.insert(tochange, '02;A;B;C\n')
    content = "".join(content)
    csvfile.seek(0)
    csvfile.truncate(0)     # Erase content
    csvfile.write(content)

Do you agree that the second solution is more efficient ? Do you have any improvement, or better way to proceed ?

EDIT : The number of character in the line can vary.

EDIT 2 : I'm apparently obliged to read and rewrite everything, if I don't want to use padding. A possible solution would be a database-like solution, I will consider it for the future.

If I had to choose between those 2 solutions, which one would be the best performance-wise ?

Answer 1

As the caracter in the line may vary, I either have to read/write the whole file or; as @tobias_k said, use seek() to come back to the begining of the line and:

• If the line is shorter, write just the line and pad with spaces;
• If same length, write just the line;
• If it's longer re-write that line and the following.

I want to avoid using padding so I used time.perf_counter() to measure exec time of both codes, and the second solution appears to be (almost 2*) faster (CSV of 10 000 lines, match at the 6 000th).

One alternative would be to migrate to a relational database .