python syntax mess: name is not defined

Question

I've been learning from 'Learn Python the Hard Way' and this particular piece of code gives me a lot of headache:

def break_words(stuff):
    """This function will break up words for us."""
    words = stuff.split(' ')
    return words

def sort_words(words):
    """Sort the words."""
    return sorted(words)

def print_first_word(words):
    """Prints the first word after popping it off."""
    word = words.pop(0)
    print word

def print_last_word(words):
    """Prints the last word after popping it off."""
    word = words.pop(-1)
    print word

def sort_sentence(sentence):
    """Takes in a full sentence and returns the sorted words."""
    words = brea_words(sentence)
    return sort_words(words)

def print_first_and_last(sentence):
    """Prints the first and last words of the sentence."""
    words = break_words(sentence)
    print_first_word(words)
    print_last_word(words)

def print_first_and_last_sorted(sentence):
    """Sorts the words then prints the first and last one."""
    words = sort_sentence(sentence)
    print_first_word(words)
    print_last_word(words)

Once the module is imported I get errors:

>>> import ex25
>>> sentence = "All good things come to those who wait."
>>> words = ex25.break_words(sentence)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "ex25.py", line 4, in break_words
    return words
NameError: global name 'words' is not defined

Where did I go wrong? I checked the code millions of times...

Why not have break_words just return stuff.split(' ')? Doesn't explain the error, but gets you closer to working code... — Scott Hunter, May 09 '12 at 20:44
Note in `sort_sentence()` you have a typo `brea_words()` instead of `break_words()`. — Michael Berkowski, May 09 '12 at 20:44
Think @JakobBowyer might be right - this should work (despite the error in `sort_sentence`) - so you probably have an old `.pyc` that isn't being removed for some reason, so the correct code is not being called. — Hamish, May 09 '12 at 20:45
Its compiled python code. Its kinda a cheat copy of your python code that executes and imports slightly faster — Jakob Bowyer, May 09 '12 at 20:47
@alkopop79 What are pyc files: http://stackoverflow.com/questions/2998215/if-python-is-interpreted-what-are-pyc-files — Hamish, May 09 '12 at 20:47
You don't need to delete the `.pyc` file. Just save your `.py` file again and Python will recompile. Your code looks fine and there should not be an error in `break_words`. Make sure to restart the Python interpreter (or use `reload()`) after you change the source file. — Ferdinand Beyer, May 09 '12 at 20:52
Just had to move it to a different folder. Thanks for the suggestions! — alkopop79, May 09 '12 at 20:56

score 5 · Answer 1 · answered May 09 '12 at 20:51

5

Have you tried running

reload(ex25)

? If you import a file, then change that file, the python process doesn't know that you changed it. You have to either restart, or tell it to look at the module again.

answered May 09 '12 at 20:51

Aaron Sokoloski

71
2

score 1 · Answer 2 · answered May 09 '12 at 20:45

1

As I say in my comment I think your pyc file is being imported rather than your py code.

answered May 09 '12 at 20:45

Jakob Bowyer

33,878
8
76
91

score 0 · Answer 3 · answered May 09 '12 at 20:59

Suppose above answer is enough - you need to reload module. On the NFS filesystem I saw troubles with not recompiled python code after it was changed (and old pyc file was used). If 'reload' does not work you can try remove pyc file and restart python.

  ddzialak@pld ~$ python
  Python 2.7.2 (default, Aug 16 2011, 10:09:58)
  [GCC 4.6.1 20110714 (release)] on linux2
  Type "help", "copyright", "credits" or "license" for more information.
  >>> import ex25
  >>> sentence = "All good things come to those who wait."
  >>> words = ex25.break_words(sentence)
  >>> print words
  ['All', 'good', 'things', 'come', 'to', 'those', 'who', 'wait.']

python syntax mess: name is not defined

3 Answers3