How to remove the brackets at the beginning and the end of lines of csv files? [solved] (differences between writerow and writerows for array)

Question

The csv file is like below:

[0,0,0]
[]
[1,1]
[]
[]

I tried

with open('test.csv','r') as r, open('write.csv', 'w') as w:
    for line in r:
        line = line[1:-2]
        w.write(line + '\n')

but it outcomes

0,0,0
]
1,1
]
]

which should be:

0,0,0

1,1

That was weird for the empty list line, I have to do line[1:-3] to clean the line, but for the non-empty line with line[1:-2]

Here was how I wrote data into csv file:

list = [[0,0,0],[],[1,1],[],[]]

with open ('test.csv','a') as w:
    w = csv.writer(w, delimiter = '\n')
    w.writerow(list)
    w.close

Why are you creating the file with brackets to begin with? Just do `csv.writer(w).writerows(yourlist)`. (Note `writerows()` is plural when writing multiple rows.) Also no need for `w.close()` which you forgot the parenthesis to. The with-statement takes care of closing the file. — Steven Rumbalski, Mar 05 '20 at 21:21
Design issue aside, is the question itself not a duplicate of https://stackoverflow.com/questions/1894269/convert-string-representation-of-list-to-list ? — AMC, Mar 06 '20 at 01:27
@AMC To me, the outcome of this post was not about how to write data to csv or how to remove specific character as I thought before, but made me realized where the problem actually was. — heisthere, Mar 06 '20 at 09:02

Barmar · Answer 1 · 2020-03-05T21:33:17.850

0

Use rstrip() and lstrip() to remove specific characters from the dns.

line = line.lstrip('[').rstrip(']\n ')

This removes the [ at the beginning and the ] and newline at the end.

edited Mar 05 '20 at 21:33

answered Mar 05 '20 at 21:20

Barmar

596,455
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393
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that outcomes `]` as well for a empty list line – heisthere Mar 05 '20 at 21:28
1

I just tried with `line = '[]\n'` and the result was `''` – Barmar Mar 05 '20 at 21:31

score 0 · Answer 2 · answered Mar 05 '20 at 21:32

As mentioned, the problem is in the writing of the file in the first place. If this list only has a few base types (int, string, etc), you can use ast.literal_eval to build the list again

>>> import ast
>>> with open("test.csv") as f:
...     mylist = [ast.literal_eval(line) for line in f]
... 
>>> mylist
[[0, 0, 0], [], [1, 1], [], [], [0, 0, 0], [], [1, 1], [], []]

How to remove the brackets at the beginning and the end of lines of csv files? [solved] (differences between writerow and writerows for array)

2 Answers2