How do I create a CSV file from database in Python

问题:

I have a Sqlite 3 and/or MySQL table named "clients"..

Using python 2.6, How do I create a csv file named Clients100914.csv with headers? excel dialect...

The Sql execute: select * only gives table data, but I would like complete table with headers.

How do I create a record set to get table headers. The table headers should come directly from sql not written in python.

w = csv.writer(open(Fn,'wb'),dialect='excel')
#w.writelines("header_row")
#Fetch into sqld
w.writerows(sqld)

This code leaves me with file open and no headers. Also cant get figure out how to use file as log.

回答1:

import csv
import sqlite3

from glob import glob; from os.path import expanduser
conn = sqlite3.connect( # open "places.sqlite" from one of the Firefox profiles
    glob(expanduser('~/.mozilla/firefox/*/places.sqlite'))[0]
)
cursor = conn.cursor()
cursor.execute("select * from moz_places;")
#with open("out.csv", "w", newline='') as csv_file:  # Python 3 version    
with open("out.csv", "wb") as csv_file:              # Python 2 version
    csv_writer = csv.writer(csv_file)
    csv_writer.writerow([i[0] for i in cursor.description]) # write headers
    csv_writer.writerows(cursor)

PEP 249 (DB API 2.0) has more information about cursor.description.

回答2:

Using the csv module is very straight forward and made for this task.

import csv
writer = csv.writer(open("out.csv", 'w'))
writer.writerow(['name', 'address', 'phone', 'etc'])
writer.writerow(['bob', '2 main st', '703', 'yada'])
writer.writerow(['mary', '3 main st', '704', 'yada'])

Creates exactly the format you're expecting.

回答3:

You can easily create it manually, writing a file with a chosen separator. You can also use csv module.

If it's from database you can alo just use a query from your sqlite client :

sqlite <db params> < queryfile.sql > output.csv

Which will create a csv file with tab separator.

回答4:

How to extract the column headings from an existing table:

You don't need to parse an SQL "create table" statement. This is fortunate, as the "create table" syntax is neither nice nor clean, it is warthog-ugly.

You can use the table_info pragma. It gives you useful information about each column in a table, including the name of the column.

Example:

>>> #coding: ascii
... import sqlite3
>>>
>>> def get_col_names(cursor, table_name):
...     results = cursor.execute("PRAGMA table_info(%s);" % table_name)
...     return [row[1] for row in results]
...
>>> def wrong_way(cur, table):
...     import re
...     cur.execute("SELECT sql FROM sqlite_master WHERE name=?;", (table, ))
...     sql = cur.fetchone()[0]
...     column_defs = re.findall("[(](.*)[)]", sql)[0]
...     first_words = (line.split()[0].strip() for line in column_defs.split(','))
...     columns = [word for word in first_words if word.upper() != "CONSTRAINT"]
...     return columns
...
>>> conn = sqlite3.connect(":memory:")
>>> curs = conn.cursor()
>>> _ignored = curs.execute(
...     "create table foo (id integer, name text, [haha gotcha] text);"
...     )
>>> print get_col_names(curs, "foo")
[u'id', u'name', u'haha gotcha']
>>> print wrong_way(curs, "foo")
[u'id', u'name', u'[haha'] <<<<<===== WHOOPS!
>>>

Other problems with the now-deleted "parse the create table SQL" answer:

1. Stuffs up with e.g. create table test (id1 text, id2 int, msg text, primary key(id1, id2)) ... needs to ignore not only CONSTRAINT, but also keywords PRIMARY, UNIQUE, CHECK and FOREIGN (see the create table docs).

2. Needs to specify re.DOTALL in case there are newlines in the SQL.

3. In line.split()[0].strip() the strip is redundant.

回答5:

This is simple and works fine for me.

Lets say you have already connected to your database table and also got a cursor object. So following on on from that point.

import csv
curs = conn.cursor()
curs.execute("select * from oders")
m_dict = list(curs.fetchall())

with open("mycsvfile.csv", "wb") as f:
    w = csv.DictWriter(f, m_dict[0].keys())
    w.writerow(dict((fn,fn) for fn in m_dict[0].keys()))
    w.writerows(m_dict)

回答6:

unless i'm missing something, you just want to do something like so...

f = open("somefile.csv")
f.writelines("header_row")

logic to write lines to file (you may need to organize values and add comms or pipes etc...)

f.close()

回答7:

You seem to be familiar with excel and want to stay close to it. Might I suggest trying PyExcelerator?