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Simple code is confusing me
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I recently bought a book on Python, and I'm working my way through it. However, I've come to a very simple program, but I can't understand a certain part of the code. Can someone explain?
OK, pretty simple. But here's the part that confuses me.
Ok, I understand what it does. I just don't understand why. It just adds the ending to the month. September 11th, etc. But what's with the + 17 multiplied by 'th' -- + 7 multiplied by 'th'? This is really driving me nuts, and I know the answer is right in front of me, which makes it even worse. Not just the + 17 * ['th'] -- + 7 * ['th'], but the whole thing. Can someone please explain how and why this code works?
Thanks in advance, everyone. I'd be lost without you guys.
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# Print out a date, given year, month, and day as numbers
months = [
'January',
'February',
'March',
'April',
'May',
'June',
'July',
'August',
'September',
'October',
'November',
'December'
]
# A list with one ending for each number from 1 to 31
endings = ['st', 'nd', 'rd'] + 17 * ['th'] \
+ ['st', 'nd', 'rd'] + 7 * ['th'] \
+ ['st']
year = raw_input('Year: ')
month = raw_input('Month (1-12): ')
day = raw_input('Day (1-31): ')
month_number = int(month)
day_number = int(day)
# Remember to subtract 1 from month and day to get a correct index
month_name = months[month_number-1]
ordinal = day + endings[day_number-1]
print month_name + ' ' + ordinal + ', ' + year
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# A list with one ending for each number from 1 to 31
endings = ['st', 'nd', 'rd'] + 17 * ['th'] \
+ ['st', 'nd', 'rd'] + 7 * ['th'] \
+ ['st']
Thanks in advance, everyone. I'd be lost without you guys.
Python Syntax (Toggle Plain Text)
The 17 takes care of the first 17 consecutive 'th' ocurrances & the 7 takes care of the next series.
HTH
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Join Date: Jan 2006
Posts: 237
Reputation: 
Solved Threads: 33
Posting Whiz in Training
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Originally Posted by sanoski 
..
Ok, I understand what it does. I just don't understand why. It just adds the ending to the month. September 11th, etc. But what's with the + 17 multiplied by 'th' -- + 7 multiplied by 'th'? This is really driving me nuts, and I know the answer is right in front of me, which makes it even worse. Not just the + 17 * ['th'] -- + 7 * ['th'], but the whole thing. Can someone please explain how and why this code works?
...
- String
- List
- Tuples
some of the sequence type operators. Below list is applicable to *all* types of sequence.
Python Syntax (Toggle Plain Text)
endings = ['st', 'nd', 'rd'] + 17 * ['th'] \ + ['st', 'nd', 'rd'] + 7 * ['th'] \ + ['st']
breaking above expression,
>>> endings = ['st', 'nd', 'rd'] + ['th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th'] + ['st', 'nd', 'rd'] + ['th', 'th', 'th', 'th', 'th', 'th', 'th'] + ['st'] >>> endings ['st', 'nd', 'rd', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'st', 'nd', 'rd', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'st'] >>> type(endings) <type 'list'>
hope you understand.
katharnakh.
Last edited by katharnakh; Apr 24th, 2008 at 2:13 am.
Thanks a lot everyone. This cleared it up perfectly. I think I was confusing myself trying to associate the code with the month. I should have known the month was irrelevant. What I should have been focusing on was the days. The multiplying of strings kind of threw me.
But after reading these well delivered answers, it makes perfect sense. As is expected, the code is simply executed in order (obviously). So another way it could be expressed is to forget the month altogether for a moment, and just focus on 1 through 31.
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So it could be explained like this. It starts with assigning the months, 'January through December', into the variable "months". The next sequence which confused me, simply sets up another variable with the days 1 through 31, each one named appropriately. Starting with 'first, second, and third', then followed by 17 'th's (fourth, fifth, sixth, seventh, and so on). then another second, third, and fourth, then seven more 'th's for the twenty fourth through the thirtieth, and finally ending on the last 'st' for the 31st.
Beautiful. Thanks a lot, you guys
But after reading these well delivered answers, it makes perfect sense. As is expected, the code is simply executed in order (obviously). So another way it could be expressed is to forget the month altogether for a moment, and just focus on 1 through 31.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
So it could be explained like this. It starts with assigning the months, 'January through December', into the variable "months". The next sequence which confused me, simply sets up another variable with the days 1 through 31, each one named appropriately. Starting with 'first, second, and third', then followed by 17 'th's (fourth, fifth, sixth, seventh, and so on). then another second, third, and fourth, then seven more 'th's for the twenty fourth through the thirtieth, and finally ending on the last 'st' for the 31st.
Beautiful. Thanks a lot, you guys
Last edited by sanoski; Apr 24th, 2008 at 5:22 am.
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Join Date: Jul 2005
Posts: 1,221
Reputation:
Solved Threads: 138
When you see code like this, sometimes it's enlightning to print out the variable for test. Yes, you can multiply lists.
Should you find Irony, you can keep her!
Okay dude, Im not actually here to help, but I have a friendly suggestion:
don't ever say simple python code confuses you if you'd like to be taken seriously. I came in here expecting to read a stupid person's rant. Of course, your problem wasn't being confused by simple python code, just being thrown off by one of the language features.
By the way, I hope you enjoy python as much as I do.
Happy coding.
don't ever say simple python code confuses you if you'd like to be taken seriously. I came in here expecting to read a stupid person's rant. Of course, your problem wasn't being confused by simple python code, just being thrown off by one of the language features.
By the way, I hope you enjoy python as much as I do.
Happy coding.
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Originally Posted by scru
Okay dude, Im not actually here to help, but I have a friendly suggestion:
don't ever say simple python code confuses you if you'd like to be taken seriously. I came in here expecting to read a stupid person's rant. Of course, your problem wasn't being confused by simple python code, just being thrown off by one of the language features.
By the way, I hope you enjoy python as much as I do.
Happy coding.
"I'm tired." | "I lost my glasses." | "My contacts fell out." | "I can't turn on my other computer that has all my notes." | "The dog ate ate my power supply again."
If I did something like that, people really wouldn't take me seriously. However, you do have a point. I probably should have been more descriptive with my title. In the future I'll choose my words more carefully.
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