Python中的哈希图

问题:Python中的哈希图

我想在Python中实现HashMap。我想请用户输入。根据他的输入,我正在从HashMap中检索一些信息。如果用户输入HashMap的键,我想检索相应的值。

如何在Python中实现此功能?

HashMap<String,String> streetno=new HashMap<String,String>();
   streetno.put("1", "Sachin Tendulkar");
   streetno.put("2", "Dravid");
   streetno.put("3","Sehwag");
   streetno.put("4","Laxman");
   streetno.put("5","Kohli")

I want to implement a HashMap in Python. I want to ask a user for an input. depending on his input I am retrieving some information from the HashMap. If the user enters a key of the HashMap, I would like to retrieve the corresponding value.

How do I implement this functionality in Python?

HashMap<String,String> streetno=new HashMap<String,String>();
   streetno.put("1", "Sachin Tendulkar");
   streetno.put("2", "Dravid");
   streetno.put("3","Sehwag");
   streetno.put("4","Laxman");
   streetno.put("5","Kohli")

回答 0

Python字典是一种内置类型,支持键值对。

streetno = {"1": "Sachin Tendulkar", "2": "Dravid", "3": "Sehwag", "4": "Laxman", "5": "Kohli"}

以及使用dict关键字:

streetno = dict({"1": "Sachin Tendulkar", "2": "Dravid"}) 

要么:

streetno = {}
streetno["1"] = "Sachin Tendulkar" 

Python dictionary is a built-in type that supports key-value pairs.

streetno = {"1": "Sachin Tendulkar", "2": "Dravid", "3": "Sehwag", "4": "Laxman", "5": "Kohli"}

as well as using the dict keyword:

streetno = dict({"1": "Sachin Tendulkar", "2": "Dravid"}) 

or:

streetno = {}
streetno["1"] = "Sachin Tendulkar" 

回答 1

您想要的(在最初提出问题时)只是一个提示。提示:在Python中,您可以使用字典

All you wanted (at the time the question was originally asked) was a hint. Here’s a hint: In Python, you can use dictionaries.


回答 2

它是Python内置的。参见字典

根据您的示例:

streetno = {"1": "Sachine Tendulkar",
            "2": "Dravid",
            "3": "Sehwag",
            "4": "Laxman",
            "5": "Kohli" }

然后,您可以像这样访问它:

sachine = streetno["1"]

还值得一提:它可以使用任何非可变数据类型作为键。也就是说,它可以使用元组,布尔值或字符串作为键。

It’s built-in for Python. See dictionaries.

Based on your example:

streetno = {"1": "Sachine Tendulkar",
            "2": "Dravid",
            "3": "Sehwag",
            "4": "Laxman",
            "5": "Kohli" }

You could then access it like so:

sachine = streetno["1"]

Also worth mentioning: it can use any non-mutable data type as a key. That is, it can use a tuple, boolean, or string as a key.


回答 3

streetno = { 1 : "Sachin Tendulkar",
            2 : "Dravid",
            3 : "Sehwag",
            4 : "Laxman",
            5 : "Kohli" }

并获取值:

name = streetno.get(3, "default value")

要么

name = streetno[3]

那就是使用数字作为键,在数字两边加上引号以使用字符串作为键。

streetno = { 1 : "Sachin Tendulkar",
            2 : "Dravid",
            3 : "Sehwag",
            4 : "Laxman",
            5 : "Kohli" }

And to retrieve values:

name = streetno.get(3, "default value")

Or

name = streetno[3]

That’s using number as keys, put quotes around the numbers to use strings as keys.


回答 4

哈希图是Python内置的,它们称为字典

streetno = {}                        #create a dictionary called streetno
streetno["1"] = "Sachin Tendulkar"   #assign value to key "1"

用法:

"1" in streetno                      #check if key "1" is in streetno
streetno["1"]                        #get the value from key "1"

请参阅文档以获取更多信息,例如内置方法等。它们很棒,并且在Python程序中非常常见(毫不奇怪)。

Hash maps are built-in in Python, they’re called dictionaries:

streetno = {}                        #create a dictionary called streetno
streetno["1"] = "Sachin Tendulkar"   #assign value to key "1"

Usage:

"1" in streetno                      #check if key "1" is in streetno
streetno["1"]                        #get the value from key "1"

See the documentation for more information, e.g. built-in methods and so on. They’re great, and very common in Python programs (unsurprisingly).


回答 5

这是使用python实现的Hash Map的实现。为简单起见,Hash Map的大小固定为16。可以轻松更改。重新哈希不在此代码范围内。

class Node:
    def __init__(self, key, value):
        self.key = key
        self.value = value
        self.next = None

class HashMap:
    def __init__(self):
        self.store = [None for _ in range(16)]
    def get(self, key):
        index = hash(key) & 15
        if self.store[index] is None:
            return None
        n = self.store[index]
        while True:
            if n.key == key:
                return n.value
            else:
                if n.next:
                    n = n.next
                else:
                    return None
    def put(self, key, value):
        nd = Node(key, value)
        index = hash(key) & 15
        n = self.store[index]
        if n is None:
            self.store[index] = nd
        else:
            if n.key == key:
                n.value = value
            else:
                while n.next:
                    if n.key == key:
                        n.value = value
                        return
                    else:
                        n = n.next
                n.next = nd

hm = HashMap()
hm.put("1", "sachin")
hm.put("2", "sehwag")
hm.put("3", "ganguly")
hm.put("4", "srinath")
hm.put("5", "kumble")
hm.put("6", "dhoni")
hm.put("7", "kohli")
hm.put("8", "pandya")
hm.put("9", "rohit")
hm.put("10", "dhawan")
hm.put("11", "shastri")
hm.put("12", "manjarekar")
hm.put("13", "gupta")
hm.put("14", "agarkar")
hm.put("15", "nehra")
hm.put("16", "gawaskar")
hm.put("17", "vengsarkar")
print(hm.get("1"))
print(hm.get("2"))
print(hm.get("3"))
print(hm.get("4"))
print(hm.get("5"))
print(hm.get("6"))
print(hm.get("7"))
print(hm.get("8"))
print(hm.get("9"))
print(hm.get("10"))
print(hm.get("11"))
print(hm.get("12"))
print(hm.get("13"))
print(hm.get("14"))
print(hm.get("15"))
print(hm.get("16"))
print(hm.get("17"))

输出:

sachin
sehwag
ganguly
srinath
kumble
dhoni
kohli
pandya
rohit
dhawan
shastri
manjarekar
gupta
agarkar
nehra
gawaskar
vengsarkar

Here is the implementation of the Hash Map using python For the simplicity hash map is of a fixed size 16. This can be changed easily. Rehashing is out of scope of this code.

class Node:
    def __init__(self, key, value):
        self.key = key
        self.value = value
        self.next = None

class HashMap:
    def __init__(self):
        self.store = [None for _ in range(16)]
    def get(self, key):
        index = hash(key) & 15
        if self.store[index] is None:
            return None
        n = self.store[index]
        while True:
            if n.key == key:
                return n.value
            else:
                if n.next:
                    n = n.next
                else:
                    return None
    def put(self, key, value):
        nd = Node(key, value)
        index = hash(key) & 15
        n = self.store[index]
        if n is None:
            self.store[index] = nd
        else:
            if n.key == key:
                n.value = value
            else:
                while n.next:
                    if n.key == key:
                        n.value = value
                        return
                    else:
                        n = n.next
                n.next = nd

hm = HashMap()
hm.put("1", "sachin")
hm.put("2", "sehwag")
hm.put("3", "ganguly")
hm.put("4", "srinath")
hm.put("5", "kumble")
hm.put("6", "dhoni")
hm.put("7", "kohli")
hm.put("8", "pandya")
hm.put("9", "rohit")
hm.put("10", "dhawan")
hm.put("11", "shastri")
hm.put("12", "manjarekar")
hm.put("13", "gupta")
hm.put("14", "agarkar")
hm.put("15", "nehra")
hm.put("16", "gawaskar")
hm.put("17", "vengsarkar")
print(hm.get("1"))
print(hm.get("2"))
print(hm.get("3"))
print(hm.get("4"))
print(hm.get("5"))
print(hm.get("6"))
print(hm.get("7"))
print(hm.get("8"))
print(hm.get("9"))
print(hm.get("10"))
print(hm.get("11"))
print(hm.get("12"))
print(hm.get("13"))
print(hm.get("14"))
print(hm.get("15"))
print(hm.get("16"))
print(hm.get("17"))

Output:

sachin
sehwag
ganguly
srinath
kumble
dhoni
kohli
pandya
rohit
dhawan
shastri
manjarekar
gupta
agarkar
nehra
gawaskar
vengsarkar

回答 6

class HashMap:
    def __init__(self):
        self.size = 64
        self.map = [None] * self.size

    def _get_hash(self, key):
        hash = 0

        for char in str(key):
            hash += ord(char)
        return hash % self.size

    def add(self, key, value):
        key_hash = self._get_hash(key)
        key_value = [key, value]

        if self.map[key_hash] is None:
            self.map[key_hash] = list([key_value])
            return True
        else:
            for pair in self.map[key_hash]:
                if pair[0] == key:
                    pair[1] = value
                    return True
                else:
                    self.map[key_hash].append(list([key_value]))
                    return True

    def get(self, key):
        key_hash = self._get_hash(key)
        if self.map[key_hash] is not None:
            for pair in self.map[key_hash]: 
                if pair[0] == key:
                    return pair[1]
        return None

    def delete(self, key):
        key_hash = self._get_hash(key)

        if self.map[key_hash] is None :
            return False
        for i in range(0, len(self.map[key_hash])):
            if self.map[key_hash][i][0] == key:
                self.map[key_hash].pop(i)
                return True

    def print(self):

        print('---Phonebook---')
        for item in self.map:
            if item is not None:
                print(str(item))

h = HashMap()
class HashMap:
    def __init__(self):
        self.size = 64
        self.map = [None] * self.size

    def _get_hash(self, key):
        hash = 0

        for char in str(key):
            hash += ord(char)
        return hash % self.size

    def add(self, key, value):
        key_hash = self._get_hash(key)
        key_value = [key, value]

        if self.map[key_hash] is None:
            self.map[key_hash] = list([key_value])
            return True
        else:
            for pair in self.map[key_hash]:
                if pair[0] == key:
                    pair[1] = value
                    return True
                else:
                    self.map[key_hash].append(list([key_value]))
                    return True

    def get(self, key):
        key_hash = self._get_hash(key)
        if self.map[key_hash] is not None:
            for pair in self.map[key_hash]: 
                if pair[0] == key:
                    return pair[1]
        return None

    def delete(self, key):
        key_hash = self._get_hash(key)

        if self.map[key_hash] is None :
            return False
        for i in range(0, len(self.map[key_hash])):
            if self.map[key_hash][i][0] == key:
                self.map[key_hash].pop(i)
                return True

    def print(self):

        print('---Phonebook---')
        for item in self.map:
            if item is not None:
                print(str(item))

h = HashMap()

回答 7

在这种情况下,Python Counter也是一个不错的选择:

from collections import Counter

counter = Counter(["Sachin Tendulkar", "Sachin Tendulkar", "other things"])

print(counter)

这将返回一个字典,其中包含列表中每个元素的计数:

Counter({'Sachin Tendulkar': 2, 'other things': 1})

Python Counter is also a good option in this case:

from collections import Counter

counter = Counter(["Sachin Tendulkar", "Sachin Tendulkar", "other things"])

print(counter)

This returns a dict with the count of each element in the list:

Counter({'Sachin Tendulkar': 2, 'other things': 1})

回答 8

在python中,您将使用字典。

这是python中非常重要的类型,经常使用。

您可以轻松创建一个

name = {}

字典有很多方法:

# add entries:
>>> name['first'] = 'John'
>>> name['second'] = 'Doe'
>>> name
{'first': 'John', 'second': 'Doe'}

# you can store all objects and datatypes as value in a dictionary
# as key you can use all objects and datatypes that are hashable
>>> name['list'] = ['list', 'inside', 'dict']
>>> name[1] = 1
>>> name
{'first': 'John', 'second': 'Doe', 1: 1, 'list': ['list', 'inside', 'dict']}

您不能影响命令的顺序。

In python you would use a dictionary.

It is a very important type in python and often used.

You can create one easily by

name = {}

Dictionaries have many methods:

# add entries:
>>> name['first'] = 'John'
>>> name['second'] = 'Doe'
>>> name
{'first': 'John', 'second': 'Doe'}

# you can store all objects and datatypes as value in a dictionary
# as key you can use all objects and datatypes that are hashable
>>> name['list'] = ['list', 'inside', 'dict']
>>> name[1] = 1
>>> name
{'first': 'John', 'second': 'Doe', 1: 1, 'list': ['list', 'inside', 'dict']}

You can not influence the order of a dict.