Writing a dictionary as .csv file, problems about number

Question

d = { 'A': 85, 'B':70, 'C':40}

I need to write it as a .csv file with the title "title,score"

I tried two methods, but both of them do not work.

#Method 1:

f= open('score.csv','w')
f.write('Title,Score\n')
a = str(d)
for item in a.strip('{}').split(','):
    item.replace(':',',')
    f.write(item)
f.close()

#When I open score.csv, I do not know why it shows nothing.

#Method 2:

f= open('score.csv','w')
f.write('Title,Score\n')

with open('score.csv','w') as f:
    for title in d.keys():
        f.write('%s,%s\n'%(title,str(d[title]))

#method 2 cannot run, I guess it is because I cannot write the number in the file? But I tried str, it still cannot run.

so, the keys would correspond to the title column, and the values to the score column? — juanpa.arrivillaga, Oct 17 '22 at 18:34
"I guess it is because I cannot write the number in the file? But I tried str, it still cannot run." What does "cannot run" mean **exactly**? It runs fine for me, if you close the unbalanced parenthesis, which I assume is a typo. Please **always provide a clear explanation fo the problem** — juanpa.arrivillaga, Oct 17 '22 at 18:35
Also, when you open the file with `'w'` mode again, it **truncates** — juanpa.arrivillaga, Oct 17 '22 at 18:36
Not a solution, but a caution: do not write CSV manually, use the [`csv`](https://docs.python.org/3/library/csv.html) module in the standard library or another, CSV-specific writer. It's much easier to make errors than most programmers expect. — Michael Ruth, Oct 17 '22 at 20:31

score 0 · Answer 1 · answered Oct 17 '22 at 18:28

0

Using pandas can do the task in single line

pip install pandas

Logic

import pandas as pd

d = { 'A': 85, 'B':70, 'C':40}

(pd.DataFrame.from_dict(data=d, orient='index')
   .to_csv('dict_con.csv', header=False))

output csv#

answered Oct 17 '22 at 18:28

Bhargav - Retarded Skills

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using pandas for this is pretty silly. The standard library already includes a `csv` module. Why wouldn't you just use that? – juanpa.arrivillaga Oct 17 '22 at 18:32

Mark Tolonen · Answer 2 · 2022-10-17T18:58:52.210

For writing a .CSV file, use the csv module. Make sure to use the newline='' parameter as documented. See this answer for why.

It doesn't matter for this simple example, but the csv module will also properly quote fields containing the column separator and escape embedded quotes. Don't re-invent the wheel and try to write a CSV manually.

import csv

d = {'A': 85, 'B': 70, 'C': 40}

with open('score.csv', 'w', newline='') as fout:
    writer = csv.writer(fout)
    writer.writerow(['title', 'score'])
    for key, value in d.items():
        writer.writerow([key, value])

    # CSV module will properly quote and escape fields as needed
    writer.writerow(['field,with,commas','field"with"quotes'])

score.csv:

title,score
A,85
B,70
C,40
"field,with,commas","field""with""quotes"

Excel:

Visual of Excel reading the file correctly

score 0 · Answer 3 · answered Oct 17 '22 at 18:51

The second iteration of your code, "Method 2", is what you want. The reason it is "not running" is because of this line:

f.write('%s,%s\n'%(title,str(d[title]))

The error you get is "unexpected end of file", and your program file is listed as the file. If you look closely you'll see that you have three open parentheses, but you have only two closed parentheses. Add a parenthesis and it almost works perfectly. What's still holding it back a bit is this:

f= open('score.csv','w')
f.write('Title,Score\n')

You're opening the file as f, writing to it, then -- without closing it -- opening another file as f, and writing new data. The buffer from the first f file object never gets written to the file so you never get the headers as part of your CSV file.

These minor modifications to your code will do the trick:

d = { 'A': 85, 'B':70, 'C':40}

# f= open('score.csv','w')    #don't need this

with open('score.csv','w') as f:
    f.write('Title,Score\n')    #moved from above
    for title in d.keys():
        f.write('%s,%s\n'%(title, d[title]))   #don't need the str()

I forgot: you don't need that str() in f.write().

score -1 · Answer 4 · answered Oct 17 '22 at 18:34

-1

An oversimplified but working solution:

csv_string = "\n".join(",".join(map(str, pair)) for pair in d.items())
#'A,85\nB,70\nC,40'

Then write the csv_string to a file.

answered Oct 17 '22 at 18:34

DYZ

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Writing a dictionary as .csv file, problems about number

4 Answers4