On 2018-12-23 19:52, Avi Gross wrote:
There are quite a few places the new pythonic way of doing things requires
extra steps to get an iterator to expand into a list so Abdul-Rahmann
probably is right that there is no easy way to get a random key from a
standard dictionary. Other than the expected answers to make a customized
dictionary or function that provides the functionality at the expense for
potentially generating a huge list of keys in memory, I offer the following
as an alternative for large dictionaries and especially if they have large
keys.
The following is a function that iterates over the dictionary one key at a
time and when it reaches a random one, it returns the key without further
evaluation. On the average, it takes N/2 iterations for N keys. Asking to
make a list(data) may be efficient in terms of time and indexing is fast but
space is used maximally unless it just points to existing storage.
Here is one way to do the function. Some might use an emum instead.
def rand_key(data):
"""Get a random key from a dict without using all of memory."""
import random
randy = random.randrange(len(data))
this = 0
for key in data:
if (this == randy):
return(key)
this += 1
[snip]
You might as well use 'enumerate' there:
def rand_key(data):
"""Get a random key from a dict without using all of memory."""
import random
randy = random.randrange(len(data))
for this, key in enumerate(data):
if this == randy:
return key
Or you could use 'islice':
def rand_key(data):
"""Get a random key from a dict without using all of memory."""
import itertools
import random
randy = random.randrange(len(data))
return list(itertools.islice(data, randy, randy + 1))[0]
--
https://mail.python.org/mailman/listinfo/python-list
