I saw this code when reading today , notice lambda It's quite ignorant , After reading a lot of materials, I realized .（ It seems that there is still a lot to learn ！！！）

def getText():
    txt = open("hamlet.txt ", "r").read()  #  When using, enter the path of the file , In order to read the file 
    
    txt = txt.lower() # Full text in lowercase 
    
    for ch in '!''#$%&()*+,-./:;<=>[email protected][\\]^_`{|}~':  #  Put all the characters in the text , Special characters are all converted to  " " ( Space )
        txt = txt.replace(ch," ")
    return txt
    
hamletTxt = getText()

words = hamletTxt.split()
counts = {}   #  Build a dictionary 

for word in words:
    counts[word] = counts.get(word,0) + 1
    
items = list(counts.items())

items.sort(key = lambda y:y[1], reverse = True)  #  key =  lambda y:y[1]  Difficult to understand 

for i in range (10):
    word, count = items[i]
    print ("{0:<10}{1:>5}".format(word, count))

lambda function ：

lambda by Python Medium 33 One of the reserved words , This reserved word defines a special function —— Anonymous functions , also called lambda function . Anonymous functions are not nameless , Instead, the function name is returned as the result of the function .

< Function name > = lambda < parameter list > : < expression >

Equivalent to the general form ：

def < Function name > (< parameter list >):
return < expression >

The standard form is like this ：sorted(d.items(), key = lambda x : x[1] )

d.items() For objects that need to be sorted
key=lambda Variable ： Variable [ dimension ], among x:x[ ] The letters can be changed at will , Sort in brackets [] Sort the dimensions inside ,[0] Sort according to the first dimension ,[1] Sort according to the second dimension ,[2] Sort according to the third dimension , By analogy .

Example 1

#  Sort the dictionary , The dimension of data is expressed in numbers 
d = {"a":15,"b":16,"c":37,"d":24,"e":39}
b=sorted(d.items(), key=lambda x: x[1])
print(b)

The result is ：

[('a', 15), ('b', 16), ('d', 24), ('c', 37),('e', 39)]

Example 2

# Sort the dictionary , The dimension of data is expressed in string 
a = [{'name':'a','age':15},{'name':'b','age':31},{'name':'c','age':28}]
b=sorted(alist,key=lambda x:x['age'],reverse=True)
print(b)

The result is ：

{'name': 'b', 'age': 31}, {'name': 'c', 'age': 28}, {'name': 'a', 'age': 15}]

Learning is a continuous process , When acquiring high-level knowledge, it feels like looking back at what you wrote before ~~ But this little bit is the testimony of your own gradual progress ！！ （ Come on, energetic workers ）