用 python 中的链接填充 sqlite3 db

Question

I'm trying to populate a database with a single column with a list of strings (links). I scraped the list and I must modify every single link before sending it to the database. This is the code:

for event in events:
    link_url = "https://www.website.com"+event+"#all"
    c.execute("INSERT INTO table (links) VALUES(?)", link_url)

I can get it working if I modify the variables and send a tuple, like this:

for event in events:
    link_url = "https://www.website.com"+event+"#all"
    link = (link_url,)
    c.execute("INSERT INTO seriea (links) VALUES(?)", link_url)

but I don't want to use this solution since I want to get a list of strings back out later:

c = connection.execute('select links from table')
list_of_urls = c.fetchall()

But this gives me a list of tuples.

This is the error I have: ProgrammingError: Incorrect number of bindings supplied. The current statement uses 1, and there are 80 supplied.

I think that's because the string characters are counted (actually more but I noticed that the number before "supplied" changes with the link fed)

Answer 1

I don't want to use this solution since I want to get a list of strings back out later:

 c = connection.execute('select links from table') list_of_urls = c.fetchall()

But this gives me a list of tuples.

The list of tuples you're getting when you do a select have nothing to do with the way you insert data. Remember, tables have two dimensions:

id	links	something	else
1	"foo"	"bar"	"baz"
2	"quux"	"herp"	"derp"

When you do a select you get a list that corresponds to the rows here. But each row has multiple fields: id , links , something , and else . Each tuple in the list contains the values for each of the fields in the table.

If you just want the URLs as a list of strings you can use a list comprehension or similar:

c = connection.execute('select links from table')
list_of_rows = c.fetchall()
list_of_strings = [row[0] for row in list_of_rows]
#                      ^ index of first element in
#                  ^^^ the tuple of values for each row

Note that you do have to provide a tuple or other sequence when you insert the data:

For the qmark style, parameters must be a sequence . For the named style, it can be either a sequence or dict instance. The length of the sequence must match the number of placeholders, or a ProgrammingError is raised. If a dict is given, it must contain keys for all named parameters.

You might be thinking of the tuple part of it the wrong way. You don't need to pass in a tuple of URLs, you need to pass in a tuple of parameters . You're not saying "the links column should contain this tuple" but rather "this tuple contains enough values to fill in the placeholders in this query".

I'd rewrite that like so:

for event in events:
    link_url = "https://www.website.com"+event+"#all"
    c.execute("INSERT INTO seriea (links) VALUES(?)", (link_url,))

This is so you can have multiple parameters, eg

c.execute(
    "INSERT INTO seriea (links, some, other) VALUES(?, ?, ?)",
    (link_url, foo, bar),
)

The current statement uses 1, and there are 80 supplied.

I think that's because the string characters are counted

Yes, that's most likely what's happening. c.execute() expects to receive a sequence, and strings are a sequence of characters.