Python-如何计算对象内部数字的出现？

Question

I need to count the number of occurrences of a number in a object. Not sure how to do it.

I can access to the values in this way:

>>> formset_sample.forms[0]._raw_value('type')
>>> '1'
>>> formset_sample.forms[1]._raw_value('type')
>>> '2'
>>> formset_sample.forms[2]._raw_value('type')
>>> '2'

This object has len() = 3:

>>> len(formset_sample.forms)
>>> 3

How can I obtain the occurrences of the number 2? The number '2' have exactly two occurences in this case.

Some clues?

Best Regards,

Answer 1

It's not clear to me what you want to achieve. But maybe the map function helps you:

 values = map(lambda x: x._raw_value('type'), formset_sample.forms)
 # alternate Syntax:
 values = [form._raw_value('type') for form in formset_sample.forms]
 print values

should give you the array

 ['1', '2', '2']

which you could feed into a Counter :

from collections import Counter
print Counter(values)

should be something like

{ '1': 1, '2': 2 }

So if you want to put it all in one line:

Counter([form._raw_value('type') for form in formset_sample.forms])["2"]

Answer 2

This should give you a list of numbers and count the number of 2s:

l = [ f._raw_value('type') for f in formset_sample.forms ]
l.count('2') # I am assuming 2 is a string, or
l.count(2)   # if the number is stored as an integer

Now you can use l to sort, slice etc.

Answer 3

this will produce a dictionary with the different types as keys and number of occurences as values:

import defaultdict
d = defaultdict(int)
for rv in formset_sample.forms:
  d[rv._raw_value_('type')] += 1

Answer 4

a = {1:1, 2:1, 3:2}
print a.values().count(1)

Answer 5

count = sum(f._raw_value('type') == '2' for f in formset_sample.forms)