CODEWITHSUNDEEP
pythoncsvtuples
CodePathLvl
CodePathLvl

Reputation: 87

Read Tuple from csv in Python

I am trying to read a row in a csv, which I have previously written. That written row looks like this when is read: ['New York', '(30,40)'] and like this: ['New York', '(30,40)'] (converts the tuple in a string).

I need to read each item from the tuple to operate with the ints, but I can't if it is read like a string because if I do something like this: tuple[0], what I get is: '(' -the first character of the string tuple-

Maybe this is a question about how I write and read the rows, which actually is this way:

def writeCSV(data,name):
  fileName = name+'.csv'
  with open(fileName, 'a') as csvfile:
     writer = csv.writer(csvfile, delimiter=',')
     writer.writerow(data)

 def readCSV(filename):
    allRows = []
    with open(filename, 'rb') as f:
       reader = csv.reader(f, delimiter=' ')
       for row in reader:
          allRows.append(row)
 return allRows

What I want is to read that tuple for row, not like a string, but like a tuple to operate with each item after. Is it possible?

Upvotes: 2

Views: 3378

Answers (2)

Jean-François Fabre
Jean-François Fabre

Reputation: 140226

since you're producing the file yourself, why not making it right from the start:

import csv

data = ['New York', (30,40)]
with open("out.csv","w",newline="") as f:
    cw=csv.writer(f)
    cw.writerow(data)    # wrong
    cw.writerow(data[:1]+list(data[1]))  # okay

the first line writes each item of data but tries to convert each item as str. tuple gets converted, where selecting another format could avoid this.

New York,"(30, 40)"

which explains the need to evaluate it afterwards.

The second write line writes 3 elements (now 3 columns), but preserves the data (except for the int part which is converted to str anyway)

New York,30,40

in that case, a simple string to integer conversion on rows does the job.

Note that csv isn't the best way to serialize mixed data. Better use json for that.

Upvotes: 1

Moinuddin Quadri
Moinuddin Quadri

Reputation: 48090

You need to use ast.literal_eval() on you tuple string as:

>>> my_file_line =  ['New York', '(30,40)']
>>> import ast
>>> my_tuple = ast.literal_eval(my_file_line[1])
>>> my_tuple[0]
30

Because currently the list you got after reading the file at index 1 is holding the valid string of the tuple format. ast.literal_eval will convert your tuple string to the tuple object and then you can access the tuple based on the index.

Upvotes: 2

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