[Python] Help with strings

[BigBear]

I decided to learn python and have been using a few recources to teach syntax and decided to try McKenzie's exercises found Here

I am on the second section (2.2)

Question 1 and 2 are similiar but question 1 has another part so I will start with question 2.

Get a file name from the user and display just the extension.

Python:

filename = raw_input ("Enter a file name: ") num = [filename.find (".",0, len(filename))] for i in range (len(filename),num):         print filename[i]

This should find where there is a . (period) and get a number then go from that number till the end of the input string.
print filename [i] should print the character in the postion of the . till the end of the string.[/url]

[Insectoid]

Why not just get the last character of the string and back up 3 spaces?

Python:

for i in range (len (filename)-3, len (filename):     print filename[i]

btw, I'm don't know any python beyond raw_input, so if something's wrong there, whatever.

[BigBear]

Yeah thanks that works well there needs to be another bracket before the :

But I am sure that is not due to a lack of python knowledge but a typo

But what if the extension is more than 3 characters like .mpeg or something. Also could someone explain what it wrong with my first attempt.

[Insectoid]

code:

for i in range (len(filename),num):

should be

code:

for i in range (num, len(filename)):

[[Gandalf]]

Or, using slicing:

code:

print filename[num:]

[BigBear]

insectoid @ Sat Mar 21, 2009 1:32 pm wrote:

code:

for i in range (len(filename),num):

should be

code:

for i in range (num, len(filename)):

Yeah I tried it that way to see the difference in errors and didn't change it back.

Gandalf @ Sat Mar 21, 2009 6:31 pm wrote:

Or, using slicing:

code:

print filename[num:]

This gives me a slightly different error

slice indices must be integers or None or have an __index__ method

As the for loop gives this error

range() integer start argument expected, got list.

I think I need to use find because for question 1 it has get full name as one raw_input and display it lastname, first name.

Python:

fname = raw_input("Enter your full name.") num = [fname.find(" ",0,len(fname))] for i in range (num,len(fname)):       print fname [i], print "", for j in range (0,num):     print fname[j],

Fixed quote.

[[Gandalf]]

You're putting []s around the fname.find() call, which makes it into a one-element list. Why are you doing that?

[Leela]

Can someone advise me whether my solution to this problem is all right?

Python:

filename = raw_input ('Enter your file: ') extention = [] index = -1 while filename[index] != ".":                 extention.append(filename[index])                 index = index-1 extention.reverse() ext = ''.join(extention) print 'Your extention is', ext

Great thanks!

[[Gandalf]]

Yes, it looks right, and it runs appropriately. However, the beauty of high level languages like Python is there's almost always a neater way of doing things.

Python:

filename = raw_input('Enter your file: ') ext = filename[filename.rfind(".") + 1:] print 'Your extention is', ext

[BigBear]

the syntax tag for python should really have a capital

[Leela]

[quote="[Gandalf] @ Sat May 02, 2009 2:53 pm"]Yes, it looks right, and it runs appropriately. However, the beauty of high level languages like Python is there's almost always a neater way of doing things.

Python:

filename = raw_input('Enter your file: ') ext = filename[filename.rfind(".") + 1:] print 'Your extention is', ext

[/quote]
Thanks! What is rfind? I only know 'find'.

[BigBear]

Quote:

rfind(...)
| S.rfind(sub [,start [,end]]) -> int
|
| Return the highest index in S where substring sub is found,
| such that sub is contained within s[start:end]. Optional
| arguments start and end are interpreted as in slice notation.
|
| Return -1 on failure.

Type help(str)

[Leela]

BigBear @ Sat May 02, 2009 4:41 pm wrote:

Quote:

rfind(...)
| S.rfind(sub [,start [,end]]) -> int
|
| Return the highest index in S where substring sub is found,
| such that sub is contained within s[start:end]. Optional
| arguments start and end are interpreted as in slice notation.
|
| Return -1 on failure.

Type help(str)

Thanks!