number of values in a list greater than a certain number

Question

I have a list of numbers and I want to get the number of times a number appears in a list that meets a certain criteria  I can use a list comprehension  or a list comprehension in a function  but I am wondering if someone has a shorter way     list of numbers j  4 5 6 7 1 3 7 5   list comprehension of values of j  gt  5 x    i for i in j if i gt 5   value of x len x    or function version def length of list list of numbers  number        x    i for i in list of numbers if j  gt  number       return len x  length of list j  5    is there an even more condensed version

User · Accepted Answer

You could do something like this    gt  gt  gt  j    4  5  6  7  1  3  7  5   gt  gt  gt  sum i  gt  5 for i in j  3   It might initially seem strange to add True to True this way  but I don t think it s unpythonic  after all  bool is a subclass of int in all versions since 2 3    gt  gt  gt  issubclass bool  int  True

User · Answer

You can create a smaller intermediate result like this    gt  gt  gt  j    4  5  6  7  1  3  7  5   gt  gt  gt  len  1 for i in j if i  gt  5   3

User · Answer

I ll add a map and filter version because why not   sum map lambda x x gt 5  j   sum 1 for   in filter lambda x x gt 5  j

User · Answer

if you are otherwise using numpy  you can save a few strokes  but i dont think it gets much faster compact than senderle s answer   import numpy as np j   np array j  sum j  gt  i

User · Answer

If you are using NumPy  as in ludaavic s answer   for large arrays you ll probably want to use NumPy s sum function rather than Python s builtin sum for a significant speedup -- e g   a  1000x speedup for 10 million element arrays on my laptop    gt  gt  gt  import numpy as np  gt  gt  gt  ten million   10   1000   1000  gt  gt  gt  x  y    np random randn ten million  for   in range 2    gt  gt  gt   timeit sum x  gt  y     time Python builtin sum function 1 loops  best of 3  24 3 s per loop  gt  gt  gt   timeit  x  gt  y  sum      wow  that was really slow  time NumPy sum method 10 loops  best of 3  18 7 ms per loop  gt  gt  gt   timeit np sum x  gt  y     time NumPy sum function 10 loops  best of 3  18 8 ms per loop    above uses IPython s  timeit  magic  for timing

User · Answer

Different way of counting by using bisect module    gt  gt  gt  from bisect import bisect  gt  gt  gt  j    4  5  6  7  1  3  7  5   gt  gt  gt  j sort    gt  gt  gt  b   5  gt  gt  gt  index   bisect j b   Find that index value  gt  gt  gt  print len j -index 3

User · Answer

A  somewhat  different way   reduce lambda acc  x  acc    1 if x  gt  5 else 0   j  0

User · Answer

You can do like this using function  l    34 56 78 2 3 5 6 8 45 6    print   quot The list    quot    str l      def count greater30 l         count   0       for i in l            if i  gt  30                count   count   1        return count print  quot Count greater than 30 is    quot    str count      count greater30 l

[python] number of values in a list greater than a certain number

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