Day7 list and dictionary jobs

Tuples and dictionaries

One 、 Correlation function

1. max、min - For maximum 、 minimum value

max( Sequence )

nums = [34, 89, 78, 65, 90, 23]
print(max(nums), min(nums))      # 90 23

2. sum - Finding the sum of elements in a number sequence

sum( Sequence )

nums = [34, 89, 78, 65, 90, 23]
print(sum(nums))        # 379

3.sorted - Sort ; Instead of changing the order of elements in the original sequence, a new list is generated

sorted( Sequence ); sorted(reverse=True)

nums = [34, 89, 78, 65, 90, 23]
new_nums = sorted(nums)
print(nums)         # [34, 89, 78, 65, 90, 23]
print(new_nums)     # [23, 34, 65, 78, 89, 90]

list . sort(); sort(reverse=True)

nums = [34, 89, 78, 65, 90, 23]
result = nums.sort()
print(nums)         # [23, 34, 65, 78, 89, 90]
print(result)       # None

4. len - Get the number of elements in the sequence

   ​ len( Sequence )

5. list - List type conversion

   list( Sequence ) - All sequences can be converted into lists ; When converting, directly convert the elements in the sequence into the elements of the list

print(list('abc'))          # ['a', 'b', 'c']
print(list(range(3)))       # [0, 1, 2]

print(list(enumerate(nums)))

Two 、 List derivation

1. List derivation - The essence is to create the expression of the list （ concise ）

Structure one ：
[ expression for Variable in Sequence ]

Structure II ：
[ expression for Variable in Sequence if Conditional statements ]

list1 = [10 for x in range(4)]
print(list1)        # [10, 10, 10, 10]

list2 = [x for x in range(4)]
print(list2)        # [0, 1, 2, 3]

list3 = [x * 2+1 for x in range(4)]
print(list3)        # [1, 3, 5, 7]

scores = [89, 67, 34, 56, 20, 90]
list4 = [x % 10 for x in scores]

2. Application of derivation

application 1： Let all elements in the sequence be transformed uniformly
[ expression for Variable in Sequence ]

application 2： Transform the elements in the sequence that meet a certain condition （ Make two different transformations according to whether a certain condition is satisfied ）
[ expression 1 if Conditional statements else expression 2 for Variable in Sequence ]

application 3： Extract the elements that meet a certain condition in the sequence （ extract 、 Delete ）
[ expression for Variable in Sequence if Conditional statements ]

[89, 67, 34, 56, 10, 90]  -> [[0, 89], [1, 67], ...]
nums = [89, 67, 34, 56, 10, 90]
new_nums = [[x, nums[x]] for x in range(len(nums))]
print(new_nums)

 practice 1： take nums Divide all even numbers in by 2
[89, 67, 34, 56, 10, 90, 35] -> [89, 67, 17, 28, 5, 45, 35]
nums = [89, 67, 34, 56, 10, 90, 35]
new_nums = [x if x % 2 else x // 2 for x in nums]     	# x//2, x
print(new_nums)

 practice 2： Delete all even numbers （ Extract all odd numbers ）
[89, 67, 34, 56, 10, 90, 35] -> [89, 67, 35]
nums = [89, 67, 34, 56, 10, 90, 35]
new_nums = [x for x in nums if x % 2]
print(new_nums)

3、 ... and 、 Ternary operator

Binocular operator ：+、-、*、… 、> 、= 、and、or
Monocular operator ：not
Ternary operator ：if-else

1.C/Java The ternary operator of language 

 Conditional statements ？ expression 1： expression 2  -    If the conditional statement holds, the whole operation result is an expression 1 Value , Otherwise, the result of the whole operation is an expression 2 Value 

2.python The trinary operator of 
 expression 1 if  Conditional statements  else  expression 2  -    If the conditional statement holds, the whole operation result is an expression 1 Value , Otherwise, the result of the whole operation is an expression 2 Value 

age = 18
if age >= 18:
    a = ' adult '
else:
    a = ' A minor '
print(a)

a = ' adult ' if age >= 18 else ' A minor '
print(a)

Four 、 Tuples

1. What tuples (tuple)

Tuples are container data types ; take () As a sign of the container , Multiple elements are separated by commas ：( Elements 1, Elements 2, Elements 3,…)
Tuples are immutable ( We can only check ); Tuple order - Subscript operation is supported
Elements ： Just like the list

1) An empty tuple

t1 = ()
print(type(t1), len(t1))   		 # <class 'tuple'> 0

2) Tuples with only one element - The only element must be followed by a comma

list1 = [12]
print(list1, type(list1), len(list1))   # [12] <class 'list'> 1
t2 = (12)
print(t2, type(t2))     # 12 <class 'int'>

t3 = (12,)
print(t3, type(t3))     # (12,) <class 'tuple'>

3. In general

t4 = (10, 34, 78)
print(t4)

4. In the absence of ambiguity , The parentheses of tuples can be omitted （ Directly separating multiple data with commas is also a tuple ）

t5 = 10, 34, 78
print(t5, type(t5))

t6 = 10, 34, 78 * 2
print(t6)

2. check - Get elements

1. The way of getting elements from lists tuples support

nums = (23, 45, 90, 78, 6, 34)
print(nums[1], nums[-5])

print('---------------------------------')
for x in nums:
    print(x)

print('---------------------------------')
for index in range(len(nums)):
    print(index, nums[index])

print('---------------------------------')
for index, item in enumerate(nums):
    print(index, item)

print('---------------------------------')
print(nums[1:])
print(nums[::-1])

2). Get elements of tuples through variables 1 - Keep the number of variables consistent with the number of elements in the tuple

point = (10, 23, 12)
x, y, z = point
print(x, y, z)

3). Get elements of tuples through variables 2
If the number of variables is less than the number of elements , Then one of the variables must be preceded by *.
When taking it, let it go first Variables get elements according to the positional relationship , Take all the rest The variable of ( In the form of a list )

info = (' Zhang San ', 18, 175, 180, 90, 67, 89)
name, age, *other = info
print(name, age, other)    #  Zhang San  18 [175, 180, 90, 67, 89]

name, *other = info
print(name, other)   #  Zhang San  [18, 175, 180, 90, 67, 89]

name, age, *other, math = info
print(name, age, math)   #  Zhang San  18 89
print(other)    # [175, 180, 90, 67]

x, *y, z, m = info
print(x, z, m)      # ' Zhang San ' 67 89
print(y)    # [18, 175, 180, 90]

*x, y, z = info
print(y, z)
print(x)

3. Tuples are immutable lists - All immutable related operation tuples in the list support

+、*
in  and not in
 Comparison operations 
 Tuples .count()、 Tuples index()
max、min、sum、sorted、len、tuple

num = [34, 89, 78, 65, 90, 23]
print(max(num))
print(min(num))
print(sum(num))

5、 ... and 、 Dictionaries

1. Define a way to save a student's information

stu = [' Xiao Ming ', 20, ' male ', 60, 89, 70, 55]
print(stu[0])

stu = {
    
    'name': ' Xiao Ming ',
    'age': 20,
    'gender': ' male ',
    ' weight ': 60,
    'math': 89,
    ' Chinese language and literature ': 70,
    ' English ': 55
}
print(stu['name'])

2. What is a dictionary （dict）
   ‘’’
   A dictionary is a container data type ; take {} As a container mark , Multiple key value pairs are separated by commas ：{ key 1: value 1, key 2: value 2, key 3: value 3,…}
   The dictionary is changeable （ Support the addition, deletion and modification ）; The dictionary is out of order （ Subscript operation is not supported ）

Element requirements ： Dictionary elements are key value pairs
key - The key must be immutable data ( for example ： Numbers 、 character string 、 Tuples ); The key is the only ;
value - No requirement
‘’’

1. An empty dictionary ：{}

d1 = {
    }
print(type(d1), len(d1), bool(d1))      # <class 'dict'> 0 False

2. Keys are immutable data

d2 = {
    1: 10, 'a': 20, (10, 20): 30}
print(d2)

# d3 = {1: 10, 'a': 20, [10, 20]: 30} #  Report errors 

3. The key is the only

d4 = {
    'a': 10, 'b': 20, 'c': 30, 'b': 40}
print(d4)   # {'a': 10, 'b': 40, 'c': 30}

4. The dictionary is out of order

print({
    'a': 10, 'b': 20} == {
    'b': 20, 'a': 10})     # True
print([10, 20] == [20, 10])     # False

3. Look up the dictionary
1） check - Get the value of the dictionary
a. Get a single value
‘’’
Dictionaries [ key ] - Get the value corresponding to the specified key in the dictionary , If the key does not exist, the program will report an error ！
Dictionaries .get( key )/ Dictionaries .get( key , The default value is ) - Get the value corresponding to the specified key in the dictionary , If the key does not exist, return None Or return to the default value
‘’’

dog = {
    'name': ' Wangcai ', 'age': 3, 'breed': ' Local dog ', 'gender': ' Bitch ', 'color': ' black '}
print(dog['name'])
print(dog['gender'])

print(dog.get('name'))

print(dog['height'])          # KeyError: 'height'
print(dog.get('height'))      # None
print(dog.get('height', 0))   # 0

b. Traverse

adopt for When looping through the dictionary , The cyclic variable gets the keys of the dictionary in turn

‘’’
for Variable in Dictionaries ：
loop
‘’’

dog = {
    'name': ' Wangcai ', 'age': 3, 'breed': ' Local dog ', 'gender': ' Bitch ', 'color': ' black '}
for key in dog:
    print(key, dog[key])

3. Dictionaries and lists in practical applications

Define a class to save information

class1 = {
    
    'name': 'python2014',
    'address': '23 teach ',
    'lecturer': {
    'name': ' Yu Ting ', 'age': 18, 'QQ': '726550822'},
    'leader': {
    'name': ' Shu Ling ', 'age': 18, 'QQ': '23425436', 'tel': '110'},
    'students': [{
    'name': 'stu1', 'school': ' Tsinghua University ', 'tel': '1123', 'linkman': {
    'name': ' Zhang San ', 'tel': '923'}},
                 {
    'name': 'stu2', 'school': ' Panzhihua College ', 'tel': '8999', 'linkman': {
    'name': ' Li Si ', 'tel': '902'}},
                 {
    'name': 'stu3', 'school': ' Chengdu University of technology ', 'tel': '678', 'linkman': {
    'name': ' Xiao Ming ', 'tel': '1123'}},
                 {
    'name': 'stu4', 'school': ' Sichuan University ', 'tel': '9900', 'linkman': {
    'name': ' floret ', 'tel': '782'}},
                 {
    'name': 'stu5', 'school': ' Southwest Jiaotong University ', 'tel': '665', 'linkman': {
    'name': ' Lao Wang ', 'tel': '009'}}
                ]
}
print('----------------------------')
# 1） Get the class name 
print(class1['name'])
print('----------------------------')
# 2） Get the instructor QQ
print(class1['lecturer']['QQ'])
# 3） Get the names and schools of all students 
for x in class1['students']:
    print(x['name'], x['school'])
# 4） Get the phone numbers of all students' contacts 
for x in class1['students']:
    print(x['linkman']['tel'])

print('--------------------------')
print(class1['leader']['QQ'])

for x in class1['students']:
    print(x['linkman']['name'])

print('-----------')
print(class1['students'][0]['linkman']['name'])

List and dictionary assignments

1. Create a list , The list is 10 Geshuzong , Ensure the order of elements in the list , Rearrange the list , And sort the list in descending order

 for example ： Randomly generated [70, 88, 91, 70, 107, 234, 91, 177, 282, 197]
		---  After de duplication  [70, 88, 91, 107, 234, 177, 282, 197]
  	----  null  [282, 234, 197, 177, 107, 91, 88, 70]

nums = [70, 88, 91, 70, 107, 234, 91, 177, 282, 197]
new_nums = []
for x in nums:
    if x not in new_nums:
        new_nums.append(x)
a = new_nums
a = sorted(a, reverse=True)
print(a)

2. Use list derivation , Complete the following requirements

a. Generate a storage 1-100 The median is 3 Data list

 The result is  [3, 13, 23, 33, 43, 53, 63, 73, 83, 93]

a = [x for x in range(3, 100, 10)]
print(a)

b. Use the list to push to yes The integers in the list are extracted

 for example ：[True, 17, "hello", "bye", 98, 34, 21] --- [17, 98, 34, 21]

nums = [True, 17, "hello", "bye", 98, 34, 21]
new_nums = [x for x in nums if type(x) == int]
print(new_nums)

c. Use list derivation Store the length of the string in the specified list

 for example  ["good", "nice", "see you", "bye"] --- [4, 4, 7, 3]

nums = ["good", "nice", "see you", "bye"]
new_nums = [len(x) for x in nums]
print(new_nums)			# [4, 4, 7, 3]

4. Have a class dictionary as follows ：

class1 = {
    
    'name': 'python2104',
    'address': '23 teach ',
    'lecturer': {
    'name': ' Yu Ting ', 'age': 18, 'QQ': '726550822'},
    'leader': {
    'name': ' Shu Ling ', 'age': 18, 'QQ': '2343844', 'tel': '110'},
    'students': [
        {
    'name': 'stu1', 'school': ' Tsinghua University ', 'tel': '1123', 'age': 18, 'score': 98, 'linkman': {
    'name': ' Zhang San ', 'tel': '923'}},
        {
    'name': 'stu2', 'school': ' Panzhihua College ', 'tel': '8999', 'age': 28, 'score': 76, 'linkman': {
    'name': ' Li Si ', 'tel': '902'}},
        {
    'name': 'stu3', 'school': ' Chengdu University of technology ', 'tel': '678', 'age': 20, 'score': 53, 'linkman': {
    'name': ' Xiao Ming ', 'tel': '1123'}},
        {
    'name': 'stu4', 'school': ' Sichuan University ', 'tel': '9900', 'age': 30, 'score': 87, 'linkman': {
    'name': ' floret ', 'tel': '782'}},
        {
    'name': 'stu5', 'school': ' Southwest Jiaotong University ', 'tel': '665', 'age': 22, 'score': 71, 'linkman': {
    'name': ' Lao Wang ', 'tel': '009'}},
        {
    'name': 'stu6', 'school': ' Chengdu University of technology ', 'tel': '892', 'age': 32, 'score': 80, 'linkman': {
    'name': ' Lao Wang 2', 'tel': '0091'}},
        {
    'name': 'stu7', 'school': ' Sichuan University ', 'tel': '431', 'age': 17, 'score': 65, 'linkman': {
    'name': ' Lao Wang 3', 'tel': '0092'}},
        {
    'name': 'stu8', 'school': ' Panzhihua College ', 'tel': '2333', 'age': 16, 'score': 32, 'linkman': {
    'name': ' Lao Wang 4', 'tel': '0093'}},
        {
    'name': 'stu9', 'school': ' Panzhihua College ', 'tel': '565', 'age': 21, 'score': 71, 'linkman': {
    'name': ' Lao Wang 5', 'tel': '0094'}}
    ]
}

1 Get class location

print(class1['name'])		# python2104

2） Get the name and phone number of the head teacher

print(class1['leader']['name'], class1['leader']['tel'])

3） Get the names and scores of all students

for x in class1['students']:
    print(x['name'], x['score'])

4） Get the names and phone numbers of all student contacts

for x in class1['students']:
    for y in x['linkman']['name']:
        print(y, end=(' '))
    for z in x['linkman']['tel']:
        print(z, end=(' '))

5） Get the highest score in the class

all_student = class1['students']
max_score = all_student[0]['score']
for stu in all_student[1:]:
    s = stu['score']
    if s >max_score:
        max_score = s
print(' The highest ：', max_score)

6） Get the name of the student with the highest score in the class

all_student = class1['students']
max_score = all_student[0]['score']
for stu in all_student[1:]:
    s = stu['score']
    if s >max_score:
        max_score = s
print(' The highest score winner ：', end='')
for stu in all_student:
    if stu['score'] == max_score:
        print(stu['name'], end='')

7） Calculate the average score of students in the class

all_student = class1['students']
sum1 = 0
for stu in all_student:
    sum1 += stu['score']
print(' average ：', sum1/len(all_student))

8） Count the number of minors in the class

all_student = class1['students']
count = 0
for stu in all_student:
    if stu ['age'] < 18:
        count += 1
print(' Number of minors :', count)

9） Count the number of people in each school with a dictionary , similar : {' Tsinghua University ': 1, ' Panzhihua College ': 3}

all_student = class1['students']
school_info = {
    }
for stu in all_student:
    school = stu['school']
    school_info[school] = school_info.get(school, 0) + 1
print(school_info)