Trying to solve old GoogleCodeJam for practice

Question

I'm working on some of the old Google Code Jam problems as practice in python since we don't use this language at my school. Here is the current problem I am working on that is supposed to just reverse the order of a string by word.

Here is my code:

import sys


f = open("B-small-practice.in", 'r')


T = int(f.readline().strip())


array = []

for i in range(T):
    array.append(f.readline().strip().split(' '))


for ar in array:
    if len(ar) > 1:
        count = len(ar) - 1
        while count > -1:
            print ar[count]
            count -= 1

The problem is that instead of printing:

test a is this

My code prints:

test
a
is
this

Please let me know how to format my loop so that it prints all in one line. Also, I've had a bit of a learning curve when it comes to reading input from a .txt file and manipulating it, so if you have any advice on different methods to do so for such problems, it would be much appreciated!

Answer 1

print by default appends a newline. If you don't want that behavior, tack a comma on the end.

    while count > -1:
        print ar[count],
        count -= 1

Note that a far easier method than yours to reverse a list is just to specify a step of -1 to a slice. (and join it into a string)

print ' '.join(array[::-1]) #this replaces your entire "for ar in array" loop 

Answer 2

There are multiple ways you can alter your output format. Here are a few:

---

One way is by adding a comma at the end of your print statement:

print ar[count],

This makes print output a space at the end instead of a newline.

---

Another way is by building up a string, then printing it after the loop:

reversed_words = ''
for ar in array:
    if len(ar) > 1:
        count = len(ar) - 1
        while count > -1:
            reversed_words += ar[count] + ' '
            count -= 1
print reversed_words

---

A third way is by rethinking your approach, and using some useful built-in Python functions and features to simplify your solution:

for ar in array:
    print ' '.join(ar[::-1])

(See str.join and slicing).

---

Finally, you asked about reading from a file. You're already doing that just fine, but you forgot to close the file descriptor after you were done reading, using f.close(). Even better, with Python 2.5+, you can use the with keyword:

array = list()
with open(filename) as f:
    T = int(f.readline().strip())
    for i in range(T):
        array.append(f.readline().strip().split(' '))

# The rest of your code here

This will close the file descriptor f automatically after the with block, even if something goes wrong while reading the file.

Answer 3

T = int(raw_input())

for t in range(T):
    print "Case #%d:" % (t+1),
    print ' '.join([w for w in raw_input().split(' ')][::-1])