On 06/12/2012 07:01 AM, Nathan Lowrie wrote:
> On Jun 9, 2012, at 1:45 PM, Paul McNett wrote:
>
>> On 6/9/12 9:49 AM, Ed Leafe wrote:
>>> On Jun 9, 2012, at 11:26 AM, John Fabiani wrote:
>>>
>>>>> I am having issue with the binary field type.
>>>> What type of issue?
>>> And what database?
>> I'm storing images to an sqlite database, I'll dig out the code. I found
>> that I
>> needed different code to store to MySQL. This shouldn't be, since Dabo's
>> supposed to
>> wrap the differences but that's all I had time to find out.
> I can do the following just fine:
>
> f = open('my/path/to/file.pdf', 'rb')
> data = f.read() # contains binary data
>
> outfile = open('file/to/write/to.pdf', 'wb')
> outfile.write(data)
>
>
> It will rewrite the data just fine. However if I store it in a binary field
> in a bizobj and try to write from the binary field, I get a unicode error.
>
> f = open('my/path/to/file.pdf', 'rb')
> data = f.read() # contains binary data
>
> bizobj.setFieldVal('file', data)
> bizobj.save()
>
> data = bizobj.getFieldVal('file')
> outfile = open('file/to/write/to.pdf', 'wb')
> outfile.write(data)
>
> This results in a
>
> UnicodeEncodeError: 'ascii' codec can't encode character: ordinal not in
> range(128)
>
> Not sure how to proceed... What data type does the binary database field
> type translate to?
>
> Also, if anyone wants to know why, I have a request to link receipts (either
> email attachments, scanned pictures, or pdfs) to an expense report so that
> they can easily be found. Storing a file location is not an option in this
> case.
>
> Regards,
>
> Nate
>
I found this:
Writing images
Some people prefer to put their images into the database, some prefer to
keep them on the file system for their applications. Technical
difficulties arise when we work with millions of images. Images are
binary data. MySQL database has a special data type to store binary data
called *BLOB* (Binary Large Object).
mysql> CREATE TABLE Images(Id INT PRIMARY KEY AUTO_INCREMENT, Data MEDIUMBLOB);
Query OK, 0 rows affected (0.06 sec)
For this example, we create a new table called Images.
#!/usr/bin/python
# -*- coding: utf-8 -*-
import MySQLdb as mdb
import sys
try:
fin = open("chrome.png")
img = fin.read()
fin.close()
except IOError, e:
print "Error %d: %s" % (e.args[0],e.args[1])
sys.exit(1)
try:
conn = mdb.connect(host='localhost',user='testuser',
passwd='test623', db='testdb')
cursor = conn.cursor()
cursor.execute("INSERT INTO Images SET Data='%s'" % \
mdb.escape_string(img))
conn.commit()
cursor.close()
conn.close()
except mdb.Error, e:
print "Error %d: %s" % (e.args[0],e.args[1])
sys.exit(1)
In the above script, we read a png image and insert it into the Images
table.
fin = open("chrome.png")
img = fin.read()
We open and read an image. The *read()* function returns the data as
string.
cursor.execute("INSERT INTO Images SET Data='%s'" % \
mdb.escape_string(img))
This string data is inserted into the table. Before doing so, it is
processed by the *escape_string()* method. It escapes a string for use
as a query parameter. This is common practice to avoid malicious sql
injection attacks.
Reading images
In the previous example, we have inserted an image into the database
table. Now we are going to read the image back from the table.
#!/usr/bin/python
# -*- coding: utf-8 -*-
import MySQLdb as mdb
import sys
try:
conn = mdb.connect(host='localhost',user='testuser',
passwd='test623', db='testdb')
cursor = conn.cursor()
cursor.execute("SELECT Data FROM Images LIMIT 1")
fout = open('image.png','wb')
fout.write(cursor.fetchone()[0])
fout.close()
cursor.close()
conn.close()
except IOError, e:
print "Error %d: %s" % (e.args[0],e.args[1])
sys.exit(1)
We read one image from the Images table.
cursor.execute("SELECT Data FROM Images LIMIT 1")
We select one record from the table.
fout = open('image.png','wb')
We open a writable binary file.
fout.write(cursor.fetchone()[0])
We fetch the data from the previous SQL statement and write it to the file.
Now we should have an image called image.png in our current directory.
We can check if it is the same image, that we have inserted into the table.
Johnf
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