CSV mit csv.reader lesen

Einführung

Eine CSV-Datei öffnen

import csv, io
sample = 'name,age,city\nAlice,30,NYC\nBob,25,LA'
reader = csv.reader(io.StringIO(sample))
for row in reader:
    print(row)

Grundlagen von csv.reader

import csv, io
data = 'a,b,c\n1,2,3\n4,5,6'
for row in csv.reader(io.StringIO(data)):
    print(row)

Die Kopfzeile überspringen

import csv, io
data = 'name,age\nAlice,30\nBob,25'
reader = csv.reader(io.StringIO(data))
header = next(reader)  # skip
for row in reader:
    print(row)

Benutzerdefiniertes Trennzeichen

import csv, io
data = 'a;b;c\n1;2;3'
for row in csv.reader(io.StringIO(data), delimiter=';'):
    print(row)

Anführungszeichen in Feldern verarbeiten

import csv, io
data = 'name,note\n"Smith, John","great guy"'
for row in csv.reader(io.StringIO(data)):
    print(row)

csv.DictReader

import csv, io
data = 'name,age\nAlice,30\nBob,25'
for row in csv.DictReader(io.StringIO(data)):
    print(row['name'], row['age'])

Typkonvertierung

import csv, io
data = 'item,price\napple,1.5\nbanana,0.75'
for row in csv.DictReader(io.StringIO(data)):
    print(row['item'], float(row['price'])*2)

Kodierung verarbeiten

# with open('data.csv', encoding='utf-8-sig', newline='') as f:
#     reader = csv.DictReader(f)
print('encoding demo')

Große CSV-Dateien

import csv, io
data = '\n'.join(f'{i},{i*2}' for i in range(1000))
reader = csv.reader(io.StringIO(data))
print(sum(int(row[0]) for row in reader))

Das Format erkennen

import csv, io
data = 'a|b|c\n1|2|3'
sniff = csv.Sniffer().sniff(data[:100])
print('delimiter:', sniff.delimiter)
for row in csv.reader(io.StringIO(data), dialect=sniff):
    print(row)

Kurztest

Zusammenfassung

Weiter geht's