select

Select 50 items from list at random Question: I have a function which reads a list of items from a file. How can I select only 50 items from the list randomly to write to another file? def randomizer(input, output=’random.txt’): query = open(input).read().split() out_file = open(output, ‘w’) random.shuffle(query) for item in query: out_file.write(item + ‘n’) …

select first column in a 3d ndarray Question: I got a simple question for python. Instead of iterating over the first line for a 3D ndarray, I want to select the whole column. So lets say:instead of: print test[0][20][33] print test[1][20][33] … I want to put something like: print test[:][20][33] But this does not work. …

python – How select.select() works? Question: Background: I’m familiar with C’s select() function. I’ve been using this function for many purposes. Most of them, if not all, for reading and writing to pipes, files, etc. I must say that I’ve never used the error list, but this is not involved in the key question. Question: …

Selecting multiple columns in a Pandas dataframe Question: How do I select columns a and b from df, and save them into a new dataframe df1? index a b c 1 2 3 4 2 3 4 5 Unsuccessful attempt: df1 = df[‘a’:’b’] df1 = df.ix[:, ‘a’:’b’] Asked By: user1234440 || Source Answers: The column …

Explicitly select items from a list or tuple Question: I have the following Python list (can also be a tuple): myList = [‘foo’, ‘bar’, ‘baz’, ‘quux’] I can say >>> myList[0:3] [‘foo’, ‘bar’, ‘baz’] >>> myList[::2] [‘foo’, ‘baz’] >>> myList[1::2] [‘bar’, ‘quux’] How do I explicitly pick out items whose indices have no specific patterns? …

Python: Tuples/dictionaries as keys, select, sort Question: Suppose I have quantities of fruits of different colors, e.g., 24 blue bananas, 12 green apples, 0 blue strawberries and so on. I’d like to organize them in a data structure in Python that allows for easy selection and sorting. My idea was to put them into a …

Django Multiple Choice Field / Checkbox Select Multiple Question: I have a Django application and want to display multiple choice checkboxes in a user’s profile. They will then be able to select multiple items. This is a simplified version of my models.py: from profiles.choices import SAMPLE_CHOICES class Profile(models.Model): user = models.ForeignKey(User, unique=True, verbose_name_(‘user’)) choice_field = …

"select" on multiple Python multiprocessing Queues? Question: What’s the best way to wait (without spinning) until something is available in either one of two (multiprocessing) Queues, where both reside on the same system? Asked By: cdleary || Source Answers: You could use something like the Observer pattern, wherein Queue subscribers are notified of state changes. …

How can I get all rows with keys provided in a list using SQLalchemy? Question: I have sequence of IDs I want to retrieve. It’s simple: session.query(Record).filter(Record.id.in_(seq)).all() Is there a better way to do it? Asked By: Cheery || Source Answers: I’d recommend to take a look at the SQL it produces. You can just …