Python: how do I convert all columns except one in a CSV to integers

Question

I have CSV files with varying number of columns. The first column is always a string, the other columns are always integers.

The first column is always "name", but the other columns can have different names - so I cannot hardcode the key values for any column except for "name".

Ideally there would be some kind of syntax/function that would allow me to do !"name" to int and then I could put something together.

Here is what I have now, it does not do the conversion to int, it just builds a dictionary.

import csv

persons = []
    database_csv = sys.argv[1]
    with open(database_csv, "r") as database:
            read_csv = csv.DictReader(database)
            for row in read_csv:
                persons.append(row)

I have found solutions to convert all to int, key (for example "name") to int, but I could not find anything that would let me convert everything except "name" to int.

Please note that I am using a dictionary, not a list. Solutions for lists are not directly useful downstream. If no viable solution for selectively changing datatypes within a dictionary without resorting to pandas exist then I will need to reconsider the dictionary approach and figure out how to make the rest of the code work.

Answer 1

I dont know if you heard about pandas. But you can used the following

import pandas as pd

df = pd.read_csv(database_csv)
persons = df.values.tolist()

Answer 2

Hope this helps,

import csv

persons = []
with open("database.csv", "r") as database:
    read_csv = csv.DictReader(database)
    for row in read_csv:
        # Type decl does nothing.
        row: dict
        print(row.keys())
        for key in row.keys():
            print(row[key])

Answer 3

Does this work?

import csv


with open(database_csv) as fp:
    csvreader = csv.reader(fp)
    headers = next(csvreader)
    name_idx = headers.index('name')
    rows = [row for row in csvreader]
    rows = [int(value) for value in row for row in rows if row.index(value) != name_idx]

Answer 4

To convert every value in a dict, except that for one certain key, you could do

converted = {k: (v if k == 'name' else int(v)) for k, v in row.items()}

Let's pick this apart:

• {k: v for k, v in... } — This is a dict comprehension , which lets us iterate over something and build a dict from the result. In this case, we expect the... to be a sequence of pairs, which we pick apart into two variables with the k, v construct.
• v if k=='name' else int(v) — we use a conditional expression to decide, for each item, what to do with it — keep it as-is or call int() on it.
• row.items()) — this gives us each element of the row dict as a (key, value) pair, which is what we said in the first point that we were expecting.

(If you have several keys that you wish to keep unchanged, you could do

excluded = set(['name', 'address', 'preferred_colour'])

and then use if k in excluded_set instead of if k=='name' ) )