Python 与 psycopg2 和 pgAdmin4 我如何检索 bytea 数据

Question

I have uploaded a jpg image with the bytes() function to the bytea field.

INSERT CODE

 conn = None
try:
    # read data from a picture
    imagen = open("imagen.jpg", "rb").read()
    # connect to the PostgresQL database
    conn = psycopg2.connect(host="localhost", database="test", user="postgres", password="admin")
    # create a new cursor object
    cur = conn.cursor()
    # execute the INSERT statement
    cur.execute("INSERT INTO nuevotest(id,data) " +
                "VALUES(%s,%s)",
                (1, bytes(imagen)))
    # commit the changes to the database
    conn.commit()
    # close the communication with the PostgresQL database
    cur.close()
except (Exception, psycopg2.DatabaseError) as error:
    print(error)
finally:
    if conn is not None:
        conn.close()

SELECT CODE:

    conn = None
try:
    conn = psycopg2.connect(host="localhost", database="test", user="postgres", password="admin")
    # create a new cursor object
    cur = conn.cursor()
    # execute the INSERT statement
    cur.execute(""" SELECT data
                    FROM nuevotest
                    WHERE id=1 """,
                )
    # commit the changes to the database
    conn.commit()
    imagen = cur.fetchall()
    print(type(imagen))
    print(imagen)

    # close the communication with the PostgresQL database
    cur.close()
except (Exception, psycopg2.DatabaseError) as error:
    print(error)
finally:
    if conn is not None:
        conn.close()

But what i was expectiong was a list or tuple with the byte code, not this:

PyCharm console with a (memory direction? idk)

I have no idea how to work with that.

Answer 1

Depends on what you are planning on doing after you retrieve the data. As @adrian_klaver said, you can use a buffer to write the output. Like this you would send it to a file:

with open(your_output_file, 'wb') as im:
    im.write(the_in_memory_data)

Using PIL you can output it to the image viewer of the system without saving it.