two python beginner questions

[texas22]

I am new to programming and am trying to teach myself python. I have two questions how do you use a for loop to print out the lines from a list with the line numbers then the word and then I also was wondering what the tag was to print out the three longest, shortest, and middle length words along with their actual lengths

[bartonc]

I am new to programming and am trying to teach myself python. I have two questions how do you use a for loop to print out the lines from a list with the line numbers then the word and then I also was wondering what the tag was to print out the three longest, shortest, and middle length words along with their actual lengths

Off the top of my head, here's the first part:

strList = ['goodbye', 'cruel', 'world']
for i, word in enumerate(strList):
    print "%d: %s" %(i, word)
 

0: goodbye
1: cruel
2: world

[texas22]

Thanks, that makes sense I couldn't find an example showing to use enumerate to number the lines of the list anywhere, this really helped. What exactly does the line print "%d: %s"%(i, word) mean?

[bartonc]

Thanks, that makes sense I couldn't find an example showing to use enumerate to number the lines of the list anywhere, this really helped. What exactly does the line print "%d: %s"%(i, word) mean?

That's called "string formatting". Inside quotes the % has special meaning. Here is the documentation.

Basically, it says print a (d)ecimal followed by a ': ' followed by a (s)tring, where the decimal is in i and the string is in word (actually the (i, word) tuple).

[bartonc]

I am new to programming and am trying to teach myself python. I have two questions how do you use a for loop to print out the lines from a list with the line numbers then the word and then I also was wondering what the tag was to print out the three longest, shortest, and middle length words along with their actual lengths

Here's a quick one for part of the second part:

>>> most = 0
>>> least = 100
>>> for i, word in enumerate(strList):
...     most = max(most, len(word))
...     least = min(least, len(word))
...     print "%d: %s" %(i, word)
...     

0: goodbye
1: cruel
2: world
>>> most
7
>>> least
5
>>>

[ghostdog74]

before enumerate, there was the long winded way

for i in range(len(mylist)):
     print "%d: %s" % ( i, mylist[i])
 

[bvdet]

I am new to programming and am trying to teach myself python. I have two questions how do you use a for loop to print out the lines from a list with the line numbers then the word and then I also was wondering what the tag was to print out the three longest, shortest, and middle length words along with their actual lengths

The first two items in the 2nd part are easy:

wordList = ['We', 'can', 'use', 'a', 'list', 'comprehension', 'to', 'create', 'the', 'length', 'list']
lenList = [len(w) for w in wordList]
wordL = wordList[lenList.index(max(lenList))]
print "The longest word is '%s'. It is %d characters long." % (wordL, len(wordL))
 
wordS = wordList[lenList.index(min(lenList))]
print "The shortest word is '%s'. It is %d characters long." % (wordS, len(wordS))

>>> The longest word is 'comprehension'. It is 13 characters long.
The shortest word is 'a'. It is 1 characters long.

The middle length word will take a little work:

def midWord(wList):
    dd = {}
    for w in wList:
        if not dd.has_key(len(w)):
            dd[len(w)] = w
    keys = dd.keys()
    keys.sort()
    return dd[keys[len(keys)/2]]
 
wordM = midWord(wordList)
print "The middle length word is '%s'. It is %d characters long." % (wordM, len(wordM))

>>> The middle length word is 'list'. It is 4 characters long.

Maybe one of the other experts can show us a better way.

[ghostdog74]

wordList = ['We', 'can', 'use', 'a', 'list', 'comprehension', 'to', 'create', 'the', 'length', 'list']
a = [(len(i),i) for i in wordList]
b=sorted(a)
print "Max length is ", b[-1]
print "Shortest length is " , b[0]
 

i don't understand middle length though.

[texas22]

It really helps seeing some examples I able to understand where everything goes and what everything means....so if I wanted to pick the 3 longest/shortest etc.. out of a list where in the code would I tell it to take 3 of the longest etc.

Thanks

[bartonc]

It really helps seeing some examples I able to understand where everything goes and what everything means....so if I wanted to pick the 3 longest/shortest etc.. out of a list where in the code would I tell it to take 3 of the longest etc.

Thanks

I really like what ghostdog74 has done here with a list comprehension. The next thing to learn about is "slice"ing of iterable objects. Here we'll slice off 3 instead of using an absolute index to the 1st and last:

wordList = ['We', 'can', 'use', 'a', 'list', 'comprehension', 'to', 'create', 'the', 'length', 'list']
a = [(len(i),i) for i in wordList]
b=sorted(a)
print "The longest three are: ", b[-3:]
print "The shortest three are " , b[:3]

[texas22]

Thanks that really helps make sense out of it all so what would the syntax be to find the 3 middle length words in a list?

[bvdet]

Thanks that really helps make sense out of it all so what would the syntax be to find the 3 middle length words in a list?

I also like what ghostdog74 did with the list comprehension:

>>> wordList = ['We', 'can', 'use', 'a', 'list', 'comprehension', 'to', 'create', 'the', 'length', 'list']
>>> a = [(len(i),i) for i in wordList]
>>> a.sort()
>>> m = len(wordList)/2
>>> print a[m-1:m+2]
[(3, 'the'), (3, 'use'), (4, 'list')]
>>>