在Python中查找字符串中每个单词的频率

编写一个Python代码来查找给定字符串中每个单词的频率。

例子：

Input :  str[] = "Apple Mango Orange Mango Guava Guava Mango" 
Output : frequency of Apple is : 1
         frequency of Mango is : 3
         frequency of Orange is : 1
         frequency of Guava is : 2

Input :  str = "Train Bus Bus Train Taxi Aeroplane Taxi Bus"
Output : frequency of Train is : 2
         frequency of Bus is : 3
         frequency of Taxi is : 2
         frequency of Aeroplane is : 1

方法 1 使用 list()：
1.使用Python中的split函数（即字符串.split()）将字符串拆分为包含单词的列表，并带有分隔符空格。

Note:
string_name.split(separator) method is used to split the string 
by specified separator(delimiter) into the list.
If delimiter is not provided then white space is a separator. 

For example:
CODE   : str='This is my book'
         str.split()
OUTPUT : ['This', 'is', 'my', 'book']

2.初始化一个新的空列表。
3.现在，如果新列表中不存在该单词，则将之前字符串中的单词附加到新列表中。
4.遍历新列表，并使用count函数（即string.count( 字符串 [iteration])）在每次迭代中找到单词的频率。

Note:
string_name.count(substring) is used to find no. of occurrence of 
substring in a given string.

For example:
CODE   : str='Apple Mango Apple'
         str.count('Apple')
         str2='Apple'
         str.count(str2)
OUTPUT : 2
         2

Python3

# Python code to find frequency of each word
def freq(str):
  
    # break the string into list of words 
    str = str.split()         
    str2 = []
  
    # loop till string values present in list str
    for i in str:             
  
        # checking for the duplicacy
        if i not in str2:
  
            # insert value in str2
            str2.append(i) 
              
    for i in range(0, len(str2)):
  
        # count the frequency of each word(present 
        # in str2) in str and print
        print('Frequency of', str2[i], 'is :', str.count(str2[i]))    
  
def main():
    str ='apple mango apple orange orange apple guava mango mango'
    freq(str)                    
  
if __name__=="__main__":
    main()             # call main function

输出：

Frequency of  apple  is :  3
Frequency of  mango  is :  3
Frequency of  orange  is :  2
Frequency of  guava  is :  1

使用 set() 的方法 2：
1.使用Python中的split函数（即字符串.split()）将字符串拆分为包含单词的列表，并带有分隔符空格。
2.使用set()方法去除重复并给出一组唯一词
3.对集合进行迭代，并使用count函数（即string.count( 字符串[iteration])）在每次迭代中找到单词的频率。

Python3

# Python3 code to find frequency of each word
# function for calculating the frequency
def freq(str):
  
    # break the string into list of words
    str_list = str.split()
  
    # gives set of unique words
    unique_words = set(str_list)
      
    for words in unique_words :
        print('Frequency of ', words , 'is :', str_list.count(words))
  
# driver code
if __name__ == "__main__":
      
    str ='apple mango apple orange orange apple guava mango mango'
      
    # calling the freq function
    freq(str)

输出：

Frequency of  apple  is :  3
Frequency of  mango  is :  3
Frequency of  orange  is :  2
Frequency of  guava  is :  1

方法 3（使用字典）

# Find frequency of each word in a string in Python
# using dictionary.
   
def count(elements):
    # check if each word has '.' at its last. If so then ignore '.'
    if elements[-1] == '.':
        elements = elements[0:len(elements) - 1]
   
    # if there exists a key as "elements" then simply
    # increase its value.
    if elements in dictionary:
        dictionary[elements] += 1
   
    # if the dictionary does not have the key as "elements" 
    # then create a key "elements" and assign its value to 1.
    else:
        dictionary.update({elements: 1})
   
   
# driver input to check the program.
   
Sentence = "Apple Mango Orange Mango Guava Guava Mango"
   
# Declare a dictionary
dictionary = {}
   
# split all the word of the string.
lst = Sentence.split()
   
# take each word from lst and pass it to the method count.
for elements in lst:
    count(elements)
   
# print the keys and its corresponding values.
for allKeys in dictionary:
    print ("Frequency of ", allKeys, end = " ")
    print (":", end = " ")
    print (dictionary[allKeys], end = " ")
    print() 
   
# This code is contributed by Ronit Shrivastava.