My first Python program!

Dev Shed Forums Sponsor:

January 28th, 2012, 01:41 PM

ViralFrost

Registered User

Join Date: Jan 2012

Posts: 13

Time spent in forums: 2 h 39 m 17 sec
Reputation Power: 0

My first Python program!

Hey everyone, I just joined this board and look forward to being a part of the community here. Last night I was bored and decided I'd learn some Python, so I created my first program last night...so here it is. Don't be too hard on me, as this is my first program (I'm sure it could be optimized and could handle exceptions and input errors)... but anyways, the program is for downloading sequenced images from websites. Here's a sample of some input:

Quote:

URL of image folder:
(edit: gave wrong url before)
http://www.gamers-globe.com/images/screenshots/world-of-warcraft/

Image prefix:
world-of-warcraft-pc-0

First image number:
1

Last image number:
15

Leading 0 (this is for images 1-9 if for example image 1 is seen as 01) (y/n):
y

Extension:
jpg

The default download folder is C:\Images
if the folder doesn't already exist, the program creates it.

There is an error right now, where if there is a leading 0, it will download 10.jpg and 010.jpg

Also, the program will only work for less than 100 images if there is a leading 0.

Anyways, here's the code:

Code:

Code:

import urllib;
import os;
import random;

os.chdir('c:\\');

if os.path.exists('C:\\Images'):
	os.chdir('C:\\Images');
else:
	os.system('mkdir Images');
	os.chdir('C:\\Images');

print('Enter URL of image folder: ');
picture_page = raw_input();

print('Enter image prefix: ');
img_prefix = raw_input();

print('Enter starting image number: ');
img_fnum = raw_input();

print('Enter last image number: ');
img_lnum = raw_input();

print('Leading 0 (y/n): ');
lead0 = raw_input();

print('Enter file extension: ');
ext = raw_input();

a = range(int(img_lnum));

for x in a:
	if lead0 == 'y':
		if x < 10:
			a[int(x)] = '0' + str(x+1);
	else:
		a[int(x)] = str(x+1);

rfolder = random.random();
rfolder = rfolder * 7397;
rfolder = str(int(rfolder));
os.system('mkdir ' + rfolder);


for x in a:
		print('Source: ' + picture_page + img_prefix + str(a[int(x)-1]) + '.' + ext);
		print('Destination: ' + os.getcwd() + '\\' + rfolder + '\\' + img_prefix + str(a[int(x)-1]) + '.' + ext);
		urllib.urlretrieve(picture_page + img_prefix + str(a[int(x)-1]) + '.' + ext, os.getcwd() + '\\' + rfolder + '\\' + img_prefix + str(a[int(x)-1]) + '.' + ext);

If you have some ideas as to how to better automate the process, or maybe how to check whether the image actually exists on the server before the program tries to download it, or any other suggestions or tips for me please let me know!
Thanks!

January 28th, 2012, 10:07 PM

b49P23TIvg

Contributing User

Join Date: Aug 2011

Posts: 1,075

Time spent in forums: 4 Weeks 1 Day 4 h 41 m 27 sec
Reputation Power: 98

A thought

Code:

if not os.path.exists(r'C:\Images'):
	os.system(r'mkdir C:\Images')
os.chdir(r'C:\Images')

new line terminates statements.
The program always changes directory, do not duplicate code.

January 28th, 2012, 10:29 PM

ViralFrost

Registered User

Join Date: Jan 2012

Posts: 13

Time spent in forums: 2 h 39 m 17 sec
Reputation Power: 0

Good call, I tried using if !os.path.exists('...'): ...
but it didn't work, good to know that I can use 'not'

January 29th, 2012, 03:48 AM

SuperOscar

Contributing User

Join Date: Jul 2007

Location: Joensuu, Finland

Posts: 285

Time spent in forums: 4 Days 4 h 28 m 58 sec
Reputation Power: 16

Some ideas

A few further ideas:

you don’t need trailing semicolons in the lines
raw_input() can take a prompt parameter, you don’t need separate print statements
you can use os.mkdir() instead of tricky os.system() calls.

January 29th, 2012, 01:01 PM

ViralFrost

Registered User

Join Date: Jan 2012

Posts: 13

Time spent in forums: 2 h 39 m 17 sec
Reputation Power: 0

Quote:

Originally Posted by SuperOscar

A few further ideas:

you don’t need trailing semicolons in the lines
raw_input() can take a prompt parameter, you don’t need separate print statements
you can use os.mkdir() instead of tricky os.system() calls.

Thanks for letting me know about the semicolons, the Tutorial I looked at for the basics was in the Python interpreter so I figured that maybe for external scripts you needed the semicolons.

I switched to using prompts with raw_input() which made the code look nice and tidy.

BTW, what's the difference between raw_input and input?

January 29th, 2012, 01:05 PM

ViralFrost

Registered User

Join Date: Jan 2012

Posts: 13

Time spent in forums: 2 h 39 m 17 sec
Reputation Power: 0

what's the difference between os.chdir(r'C:\Images') and os.chdir('C:\Images') ?

January 29th, 2012, 01:30 PM

ViralFrost

Registered User

Join Date: Jan 2012

Posts: 13

Time spent in forums: 2 h 39 m 17 sec
Reputation Power: 0

Updated code

I've made a few changes based on your recommendations. The code looks a lot neater, as does the console output. I've also fixed the problem of the script downloading 010.* and 10.* if there is a leading 0. I think I'll try to change it so that you can enter how many leading 0's there are instead of just being able to have 1, that way if there are leading 0's the script won't be limited to 99 images.

So, here's the updated code, tell me what you think or if you want to suggest some features to add, I'd appreciate it (mainly because I'd like to learn more, so implementing suggested features would be helpful for hands-on learning).

Code:

import urllib
import os
import random

os.chdir('c:\\')

if not os.path.exists(r'C:\\Images'):
	os.mkdir(r'Images')
	
os.chdir(r'C:\\Images')

picture_page = raw_input('\nEnter URL of image folder: ')
img_prefix = raw_input('Enter image prefix: ')
img_fnum = raw_input('Enter starting image number: ')
img_lnum = raw_input('Enter last image number: ')
lead0 = raw_input('Leading 0 (y/n): ')
ext = raw_input('Enter file extension: ')

a = range(int(img_lnum))

for x in a:
	if x < 9 and lead0 == 'y':
		a[int(x)] = '0' + str(x+1)
	else:
		a[int(x)] = str(x+1)

rfolder = str(int(random.random()*7384))
os.mkdir(rfolder)

print('\n----Beginning download of ' + img_lnum + ' images----\n')
for x in a:
		print('Src: ' + picture_page + img_prefix + str(a[int(x)-1]) + '.' + ext)
		print('Dst: ' + os.getcwd() + '\\' + rfolder + '\\' + img_prefix + str(a[int(x)-1]) + '.' + ext)
		urllib.urlretrieve(picture_page + img_prefix + str(a[int(x)-1]) + '.' + ext, os.getcwd() + '\\' + rfolder + '\\' + img_prefix + str(a[int(x)-1]) + '.' + ext)
		print('----Download ' + x + '/' + img_lnum + ' complete----\n')

January 29th, 2012, 01:36 PM

b49P23TIvg

Contributing User

Join Date: Aug 2011

Posts: 1,075

Time spent in forums: 4 Weeks 1 Day 4 h 41 m 27 sec
Reputation Power: 98

strings

python has many ways to write a string.

raw string retains backslash

'\\abc' == r'\abc'

unicode string
u'abc' == 'abc'

"abc" == 'abc'

'''abc''' == 'abc'

"""abc""" == 'abc'

You can answer this other question easily: ha ha I thought they are different. They are alike.

Code:

$ python
>>> ('C:\Images',r'C:\Images',)
('C:\\Images', 'C:\\Images')
>>> 'C:\Images'==r'C:\Images'
True

January 29th, 2012, 01:38 PM

ViralFrost

Registered User

Join Date: Jan 2012

Posts: 13

Time spent in forums: 2 h 39 m 17 sec
Reputation Power: 0

Nevermind, answered my own question...doesn't work

---
Would I also be able to change a[int(x)] with x, or a[int(x)-1] with int(x)-1?

Last edited by ViralFrost : January 29th, 2012 at 01:55 PM. Reason: Answered my own question

#10

January 29th, 2012, 01:48 PM

ViralFrost

Registered User

Join Date: Jan 2012

Posts: 13

Time spent in forums: 2 h 39 m 17 sec
Reputation Power: 0

Okay, so if using slashes in the input, like for web addresses or directories, I would have to use raw_input(), right?

#11

January 29th, 2012, 02:07 PM

b49P23TIvg

Contributing User

Join Date: Aug 2011

Posts: 1,075

Time spent in forums: 4 Weeks 1 Day 4 h 41 m 27 sec
Reputation Power: 98

I use python3 if I use python. Guido discarded the raw_input function. input() returns a string in python3. Then if you need to convert it to another type you convert explicitly.

#12

January 29th, 2012, 02:16 PM

SuperOscar

Contributing User

Join Date: Jul 2007

Location: Joensuu, Finland

Posts: 285

Time spent in forums: 4 Days 4 h 28 m 58 sec
Reputation Power: 16

Quote:

Originally Posted by ViralFrost

Okay, so if using slashes in the input, like for web addresses or directories, I would have to use raw_input(), right?

Yeah. BTW, in Python 3, there’s no raw_input() and input() works like Python 2’s raw_input().

You might also consider the following:

Code:

lead0 = (raw_input('Leading 0 (y/n): ').upper() == 'Y')
fmt = '{0}'
if lead0:
    fmt = '{0:02d}'
a = [fmt.format(x) for x in range(img_fnum + 1, img_lnum + 1)]

This would create the “a” list in one sweep. (It’s bad practice to change the list you’re going through in a “for” loop.)

#13

January 29th, 2012, 02:26 PM

ViralFrost

Registered User

Join Date: Jan 2012

Posts: 13

Time spent in forums: 2 h 39 m 17 sec
Reputation Power: 0

I don't understand what you're doing with fmt ( '{0}' or '{0:02d}') please explain

#14

January 29th, 2012, 02:39 PM

ViralFrost

Registered User

Join Date: Jan 2012

Posts: 13

Time spent in forums: 2 h 39 m 17 sec
Reputation Power: 0

I tried changing
a = range(int(img_lnum)) to a = range(int(img_fnum), int(img_lnum))
but now the script gives an error of cannot concat 'str' and 'int ... I tried casting a[int(x)] in the for loop as a string, but still no luck... any ideas?

#15

January 29th, 2012, 03:28 PM

Duifmeneer

Registered User

Join Date: Jan 2012

Posts: 7

Time spent in forums: 1 h 41 m 46 sec
Reputation Power: 0

Just a tip: If you write a script it might be handy if you put some comments (# 'text'). Gives better view of what is what and makes help easier.