This Python artifact can allow you to catch fish for a long time!

I dare to guarantee with my honor that after using it, your code writing efficiency will be improved!

Who is Pampy?

First of all, popularize pattern matching.

Pattern matching is to give a certain pattern and use this pattern to check whether a sequence or string conforms to this pattern. This technology is often used in natural language processing.

Pampy is a pattern matching library for Python, a library with only 150 lines. This library is elegant and efficient and worthy of being added to the basic development stack of Python coders.

Coincidentally, the program also has a JavaScript version library of the same name Pampy.js.

If you are interested, you can read the source code and copy it to more development languages.

The way to install this library is also cliché:

• pip install pampy
  

Pampy’s fancy show

Match a single character

We can use _ to match a single character:

from pampy import _,match
a=['a',1,'b',2,'c',3,'d',4]
patter = ['a',1,'b',_,'c',3,'d',4]
action=lambda x: f'b is: {x}'
print(match(a,patter,action))

The running result is:

• b is: 2
  

As can be seen from the above example, in fact we just use _ as a placeholder. When matching, find the corresponding element.

Matching Dictionary

We can match the key or value at any level in the multi-level dictionary:

from pampy import _, match
person = {
 'address': {'province': '湖北', 'city': '武汉', 'district': '东湖高新'},
 'name': '闲欢'
}
patter = {_: {_: '武汉'}}
action = lambda k1, k2: ({'k1': k1, 'k2': k2})
print(match(person, patter, action))

The running result is:

• {'k1': 'address', 'k2': 'city'}
  

Similar to the previous example, the _ placeholder is used here placeholder, and then locate the placeholder in the action to output the result.

Match the beginning and end

In the above example, we all use placeholders to occupy places, but placeholders can only match one character. The following example , we will use the two keywords HEAD and TAIL to match the beginning and end. They can match any number of characters:

from pampy import _,match,HEAD,TAIL
a=['a',1,'b',2,'c',3,'d',4]
patter = [HEAD,_,'b',2,'c',3,TAIL]
action=lambda h,m,t: ({'head':h,'middle':m,'tail':t})
print(match(a,patter,action))

Running the above example, the result is:

• {'head': 'a', 'middle': 1, 'tail': ['d', 4]}

We can see from the results that HEAD matched a character , TAIL matches two characters. When outputting, if there are multiple characters, the result will be given in the form of an array.

Summary

Pampy’s examples are very simple and everyone can understand them after reading them. By looking at a few examples, do you have a feeling: Wow, there are such artifacts!

Of course, Pampy has more than just a few ways of pattern matching, and there are more ways for everyone to explore.

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