A small example about python sorted function

I learned socket programming two days ago, and when I asked a certain expert for advice, I was rejected. I felt like I wanted to run before I even learned how to walk. The master said that for my current level, I should do some small exercises such as operating files, serial numbers, etc. to deepen my understanding. The following is a small exercise he gave me:

1. datas = [['sherry',19,'female'],['flora',21,'female'],[' june',15,'femal']], sort the output according to the first letter of the name and age respectively;

2. Output the comparison results according to the given output method, and supplement the Person class;

class_mates = {'sherry':[18,'male'],'june':[20,'female'],'flora':[19,'female'],'alina':[21,'male']}

class Person(object):

　　def __init__(self,name,age):
　　self.name = name

p1 = Person('sherry',20)
p2 = Person('june',20)


if p1<p2:
print(&#39;p1:{} less than p2:{}&#39;.format([p1.name,p1.age],[p2.name,p2.age]))
else:
print(&#39;p1:{} gte than p2:{}&#39;.format([p1.name,p1.age],[p2.name,p2.age]))

It’s so simple, I actually did it all afternoon (slap in the face)

def get_first(info):
     first_value = info[0][0]
     return first_value

 na = sorted(datas,key=get_first)
 print(na)

 def age_sort(info):
     return info[1]
 print(sorted(datas,key=age_sort))

Answer to question 2

class_mates = {'sherry':[18,'male'],'june':[20,'female'],'flora':[19,'female'],'alina':[21,'male']}

class Person(object):

    def __init__(self,name,age):
        self.name = name
        self.age = age
    def __lt__(self,others):
        if(self.age<others.age):
            return 1
        elif(self.age==others.age): 
            if(self.name[0]<others.name[0]):
                return 1
            else:
                return 0
        return 0

p1 = Person(&#39;sherry&#39;,20)
p2 = Person(&#39;june&#39;,20)


if p1<p2:
    print(&#39;p1:{} less than p2:{}&#39;.format([p1.name,p1.age],[p2.name,p2.age]))
else:
    print(&#39;p1:{} gte than p2:{}&#39;.format([p1.name,p1.age],[p2.name,p2.age]))

ViewpythonOfficial documentation , summarize the knowledge gained.

1、sorted(iterable[, key][, reverse])

Returns a reordered list, with two optional keyword arguments (specify arguments by name rather than position).

key defines a function with parameters, extracts an element of the list as a parameter of this function, and returns the value as the keyword you call. The default value is None (direct comparison of the list Element)

reverse is a Boolean value. True means to sort the elements in the list in reverse order.

2. ln(a,b), when using a

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