Turn pandas dataframe into a file-like object in memory?

Python module io(docs) has necessary tools for file-like objects.

import io

# text buffer
s_buf = io.StringIO()

# saving a data frame to a buffer (same as with a regular file):
df.to_csv(s_buf)

Edit. (I forgot) In order to read from the buffer afterwards, its position should be set to the beginning:

s_buf.seek(0)

I'm not familiar with psycopg2 but according to docs both copy_expert and copy_from can be used, for example:

cur.copy_from(s_buf, table)

(For Python 2, see StringIO.)

I had problems implementing the solution from ptrj.

I think the issue stems from pandas setting the pos of the buffer to the end.

See as follows:

from StringIO import StringIO
df = pd.DataFrame({"name":['foo','bar'],"id":[1,2]})
s_buf = StringIO()
df.to_csv(s_buf)
s_buf.__dict__

# Output
# {'softspace': 0, 'buflist': ['foo,1\n', 'bar,2\n'], 'pos': 12, 'len': 12, 'closed': False, 'buf': ''}

Notice that pos is at 12. I had to set the pos to 0 in order for the subsequent copy_from command to work

s_buf.pos = 0
cur = conn.cursor()
cur.copy_from(s_buf, tablename, sep=',')
conn.commit()