I have a CSV file and I want to bulk-import this file into my sqlite3 database using Python. the command is ".import .....". but it seems that it cannot work like this. Can anyone give me an example of how to do it in sqlite3? I am using windows just in case. Thanks
17 Answers
import csv, sqlite3
con = sqlite3.connect(":memory:") # change to 'sqlite:///your_filename.db'
cur = con.cursor()
cur.execute("CREATE TABLE t (col1, col2);") # use your column names here
with open('data.csv','r') as fin: # `with` statement available in 2.5+
# csv.DictReader uses first line in file for column headings by default
dr = csv.DictReader(fin) # comma is default delimiter
to_db = [(i['col1'], i['col2']) for i in dr]
cur.executemany("INSERT INTO t (col1, col2) VALUES (?, ?);", to_db)
con.commit()
con.close()
Creating an sqlite connection to a file on disk is left as an exercise for the reader ... but there is now a two-liner made possible by the pandas library
df = pandas.read_csv(csvfile)
df.to_sql(table_name, conn, if_exists='append', index=False)
You're right that .import is the way to go, but that's a command from the SQLite3 command line program. A lot of the top answers to this question involve native python loops, but if your files are large (mine are 10^6 to 10^7 records), you want to avoid reading everything into pandas or using a native python list comprehension/loop (though I did not time them for comparison).
For large files, I believe the best option is to use subprocess.run() to execute sqlite's import command. In the example below, I assume the table already exists, but the csv file has headers in the first row. See .import docs for more info.
subprocess.run()
from pathlib import Path
db_name = Path('my.db').resolve()
csv_file = Path('file.csv').resolve()
result = subprocess.run(['sqlite3',
str(db_name),
'-cmd',
'.mode csv',
'.import --skip 1 ' + str(csv_file).replace('\\','\\\\')
+' <table_name>'],
capture_output=True)
edit note: sqlite3's .import command has improved so that it can treat the first row as header names or even skip the first x rows (requires version >=3.32, as noted in this answer. If you have an older version of sqlite3, you may need to first create the table, then strip off the first row of the csv before importing. The --skip 1 argument will give an error prior to 3.32
Explanation
From the command line, the command you're looking for is sqlite3 my.db -cmd ".mode csv" ".import file.csv table". subprocess.run() runs a command line process. The argument to subprocess.run() is a sequence of strings which are interpreted as a command followed by all of it's arguments.
sqlite3 my.dbopens the database-cmdflag after the database allows you to pass multiple follow on commands to the sqlite program. In the shell, each command has to be in quotes, but here, they just need to be their own element of the sequence'.mode csv'does what you'd expect'.import --skip 1'+str(csv_file).replace('\\','\\\\')+' <table_name>'is the import command.
Unfortunately, since subprocess passes all follow-ons to-cmdas quoted strings, you need to double up your backslashes if you have a windows directory path.
