深入了解Python中计数器Counter的使用

class collections.Counter([iterable-or-mapping])

# A Python program to show different ways to create
# Counter
from collections import Counter
# With sequence of items
print(Counter(['B','B','A','B','C','A','B','B','A','C']))
# with dictionary
print(Counter({'A':3, 'B':5, 'C':2}))
# with keyword arguments
print(Counter(A=3, B=5, C=2))

coun = collections.Counter()

coun.update(Data)

# A Python program to demonstrate update()
from collections import Counter
coun = Counter()
coun.update([1, 2, 3, 1, 2, 1, 1, 2])
print(coun)
coun.update([1, 2, 4])
print(coun)

# Python program to demonstrate that counts in
# Counter can be 0 and negative
from collections import Counter
c1 = Counter(A=4,  B=3, C=10)
c2 = Counter(A=10, B=3, C=4)
c1.subtract(c2)
print(c1)

# An example program where different list items are
# counted using counter
from collections import Counter
# Create a list
z = ['blue', 'red', 'blue', 'yellow', 'blue', 'red']
# Count distinct elements and print Counter aobject
print(Counter(z))

from collections import Counter
my_counter = Counter('abracadabra')
print(my_counter.keys())
print(my_counter.values())
print(my_counter.items())

# Python program to demonstrate accessing of
# Counter elements
from collections import Counter
# Create a list
z = ['blue', 'red', 'blue', 'yellow', 'blue', 'red']
col_count = Counter(z)
print(col_count)
col = ['blue','red','yellow','green']
# Here green is not in col_count
# so count of green will be zero
for color in col:
	print (color, col_count[color])

# Python example to demonstrate elements() on
# Counter (gives back list)
from collections import Counter
coun = Counter(a=1, b=2, c=3)
print(coun)
print(list(coun.elements()))

# Python example to demonstrate most_elements() on
# Counter
from collections import Counter
coun = Counter(a=1, b=2, c=3, d=120, e=1, f=219)
# This prints 3 most frequent characters
for letter, count in coun.most_common(3):
	print('%s: %d' % (letter, count))