Python's Path to growth second (4) _collections series

First, to remove the number greater than 66 and less than 66 of the number

Small exercise: Requirements There is a list of lists with a set of numbers that require numbers greater than 66 and numbers less than 66 to be removed separately

AA = [11,22,33,44,55,66,77,88,99,90] dic = {} for I in AA: &nbs p;   ifi <=:         if ' K1 ' in Dic.keys ():   & nbsp;         dic[' K1 '].append (i)          else:             # Creates a list of only one element            dic[' k1 ' = [i,]   #为了规范请使用逗号     Else:         if ' K2 ' in Dic.keys ():              dic[' K2 '].append (i)          Else:             dic[' k2 '] = [I,] Print ( dic[' K1 ') Print (dic[' K2 ') #k1和k2就分别保存了大于66和小于66的结果

Second, Collections series

(1) Counter counter

Counter is a supplement to the dictionary type that is used to track the number of occurrences of a value.

PS: With all the functions of the Dictionary + own function

Example:

Import Collections
F1 = collections. Counter (' ASDWQEWQDSADSADSA ')
Print (F1)

Results:

Counter ({' A ': 4, ' d ': 4, ' s ': 4, ' Q ': 2, ' W ': 2, ' E ': 1})

#这个例子就是统计出元素出现的次数

(2) Ordered dictionary class ordereddict (dict):

Orderddict is a supplement to the dictionary type, and he remembers the order in which the dictionary elements were added, thus making the dictionary more orderly

Example:

Import Collections
F1 = collections. Ordereddict ()
F1["a"] = 3
F1["C"] = 2
F1["B"] = 1
F2 = {}
F2["a"] = 3
F2["C"] = 2
F2["B"] = 1
Print (F1,F2)

Results: ordereddict (' A ', 3), (' C ', 2), (' B ', 1)]) {' B ': 1, ' C ': 2, ' A ': 3}

From the above can be found that the dictionary with the same value to use ordereddict in order to sort by adding

Internal mechanism:

In the normal dictionary F2 such a sort:

F2 = {' B ': 1, ' C ': 2, ' A ': 3}

After using ordereddict, he generates a list to save the order in which the dictionary is added.

F1 = {' B ': 1, ' C ': 2, ' A ': 3}

F1_list = ["A", "C", "B"]

This allows you to get an ordered dictionary through a for loop

Don't be serious, huh?

(3) Default dictionary (defaultdict)

Defaultdict is a supplement to the type of dictionary, which defaults to a type for the value of the dictionary.

Import Collections
F1 = collections.defaultdict (list)
F1["A"].append (1)
Print (F1)

The above effect is equal to the following, so defaultidict is set value to default to list type
F1 = {}
F1["a"] = []
F1["A"].append (1)

(4) can be named tuple namedtuple

That is, the value of the first name, and then pass the value, mainly for the plan to think of the X, Y axis

Import Collections

Atuple = Collections.namedtuple ("Atuple", [' X ', ' y ', ' z '])
New = Atuple (A.)
Print (new)

Atuple (X=1, y=2, z=3)

(5) Bidirectional queue Collections.deque

Two-way teams are listed, for example, with a list that can fetch data from the left and right, as well as add data from the left and right.

Method:

(1) def append (self, *args, **kwargs): Add right

# Real Signature Unknown
"" "Add an element to the right side of the Dequ '" ""
Pass

(2) def appendleft (self, *args, **kwargs): Add to the left of the queue

# Real Signature Unknown
"" "Add an element to the left side of the deque." "" "
Pass

(3) Clear (Self, *args, **kwargs): Clear

Real signature Unknown
"Remove all elements from the deque." "" "
The

(4) F count (self, value): The number of elements that appear

Real signature unknown; Restored from __doc__
"" "D.count (value), integer--return number of occurrences of value" ""
0

(5) def extend (self, *args, **kwargs): Expand Right Add

# Real Signature Unknown
"" Extend the right side of the deque with elements from the iterable "" "
Pass

(6) def extendleft (self, *args, **kwargs): Extended left Add

# Real Signature Unknown
"" "Extend the left side of the deque with elements from the iterable" ""
Pass

(7) def pop (self, *args, **kwargs): remove element from right

# Real Signature Unknown
"" "Remove and return the rightmost element." "
Pass

(8) def popleft (self, *args, **kwargs): remove element from left

Real signature Unknown
"" "Remove and return the leftmost element." "
Pass

(9) def remove (self, value): Deletes the specified element

# Real Signature Unknown; Restored from __doc__
"" "D.remove (value)--Remove first occurrence of value." ""
Pass

def reverse (self): Flip

# Real Signature Unknown; Restored from __doc__
"" "D.reverse ()--Reverse *in place*" ""
Pass

Three, one-way queue

Q =queue.queue (10) Creates a one-way queue, in parentheses, the number of elements that can be placed in the queue

Q Put add element

Q Get remove Element

• Characteristics of the queue: Who goes first, who goes first?
• Stack features: Clip structure, plus first out

Python's Path to growth second (4) _collections series