The python built-in function filter

class filter(object):
 """
 filter(function or None, iterable) --> filter object

 Return an iterator yielding those items of iterable for which function(item)
 is true. If function is None, return the items that are true.
 """

filter (func iterator)

func: The value in a custom or anonymous function is a Boolean. true preserves the value taken by the function and false takes the reverse. iterator: Iterable objects.

Ex. :

Filter list [‘text_test_text’, ‘test_text_1’, ‘text_test_2’, ‘3_test_text’, ‘test_test’] As long as it contains the text string and takes it out or gets reversed.

s.rfind’text’+1

rfind() in Python3 returns the position of the last occurrence of the string, or -1 if there is no match. In the number 0 is false, the integer above 0 is true, so s. rfind’text’ will have +1, no characters found and -1+1=0.

# Filter

li = ['text_test_text', 'test_text_1', 'text_test_2', '3_test_text', 'test_test']

#  By default, the value fetched by the function is retained
print(list(filter(lambda s: s.rfind('text') + 1, li)))
#  Take the next 3 An example is 1 The sample of
print(list(filter(lambda s: not s.rfind('text') + 1, li)))

# Noe custom function

l1 = ['text_test_text', 'test_text_1', 'text_test_2', '3_test_text', 'test_test']


def distinguish(l):
 nl = []
 for s in l:
  if s.rfind("text") + 1:
   nl.append(s)
 return nl


print(distinguish(l1))

# Two Custom higher-order functions

l2 = ['text_test_text', 'test_text_1', 'text_test_2', '3_test_text', 'test_test']


def f(s):
 return s.rfind('text') + 1


def distinguish(func, array):
 nl = []
 for s in array:
  if func(s):
   nl.append(s)
 return nl


print(distinguish(f, l2))

# Three anonymous function

l3 = ['text_test_text', 'test_text_1', 'text_test_2', '3_test_text', 'test_test']


def distinguish(func, array):
 nl = []
 for s in array:
  if func(s):
   nl.append(s)
 return nl

print(distinguish(lambda s: s.rfind('text') + 1, l3))

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