替换Python列表元素的一部分

Question

I have a csv file like below:

CSV:

H1,H2,H3
A_B,C1,D
F_2j,G,p5

I'm trying to remove '_' and numbers from the first column. Here's what I've tried

for i in range(len(max(cols, key=len))):
        transposed = ([(c[i] if i<len(c) else '') for c in cols])
        str(transposed[0]).replace("_",";").split()

It did replace '_', but the original transposed still prints the same csv file. How can I replace this new column with the old? Also, how can I remove digits just from column1 to give the following output?

Desired output:

H1,H2,H3
A;B,C1,D
F;j,G,p5

Answer 1

The issue may be a basic misunderstanding of the behavior of replace - it returns a copy of the modified string, but does not modify the string in-place. To have the replacement "take", you'd have to assign it back to the original string. Consider the following:

>>> text = 'blah_blah_blah'
>>> print(text.replace('_', ';'))
blah;blah;blah
>>> print(text)
blah_blah_blah

As you can see, the original text string is untouched by the replace call. To actually modify it:

>>> text = text.replace('_', ';')
>>> print(text)
blah;blah;blah

As for eliminating numbers, you can go with the regular expression-based approach in the answer from @Hackaholic (which will nicely handle the '_' to ';' conversion as well) - I just thought there would be benefit in shedding light on the behavior the replace method for strings.

Answer 2

you can try this:

import re
with open('file.csv') as f:
    for x in f:
        print re.sub("_\d*",';',x)   # here you can store it in variable and do procession on it

output:

H1,H2,H3
A;B,C1,D
F;j,G,p5 

Answer 3

I suggest using Python's CSV Module to both read and write. This may end up simplifying a lot of the logic you already have. Make sure you are actually writing the rows to a file (I don't see that in your example code). I also suggest using regular expressions for the substitution and deletion:

sub = re.sub("_\d*", ";", my_column)
# use sub as your new column

Edit : I misread what OP wanted regarding digit removal. It's ambiguous about the rules of when to wipe the digits (only after a _ character? All digits IF there is a _?). Used OP's example output as the rule ("all digits after an _")

Answer 4

import csv
import re

with open("in.csv") as f, open("out.csv", "w") as out:
    out.write(next(f))
    r = csv.reader(f, delimiter=",")
    for row in r:
        out.write("{},{}\n".format(re.sub("_\d+|[_\d+]", ";",row[0]), ",".join(row[1:])))