Days26. Dictionary Comprehension

new_dict = { new_key : new_value for item in list }

new_dict = { new_key : new_value for (key, value) in dict.items() }

new_dict = { new_key : new_value for (key, value) in dict.items() if test }

>> item은 속성값이 아니므로 item() 괄호를 반드시 붙여야 함

 

ex) names 리스트와 random 점수를 이용해 student_scores 딕셔너리를 이름, 점수로 생성

import random
names = ['Alex', 'Kio', 'Freebee', 'Susan', 'Dave', 'Caroline', 'Beth', 'Freddie']
students_scores = {student:random.randint(0,100) for student in names}
print(students_scores)

{'Alex': 38, 'Kio': 71, 'Freebee': 59, 'Susan': 34, 'Dave': 66, 'Caroline': 2, 'Beth': 40, 'Freddie': 66}

 

 

 

 

ex) dictionary comprehension 으로 생성한 students_scores 딕셔너리를 이용해서

일정 점수 이상의 student를 dictionary comprehension을 이용해 다시 생성

import random
names = ['Alex', 'Kio', 'Freebee', 'Susan', 'Dave', 'Caroline', 'Beth', 'Freddie']
students_scores = {student:random.randint(0,100) for student in names}
print(students_scores)
for key in students_scores:
    print(students_scores[key])
#passed_students = {
#                  student:students_scores[student] for student in students_scores 
#                  if students_scores[student] >= 50
#                  }
passed_students = {
                  student:score for (student, score) in students_scores.items()
                  if score >= 50
                  }
print(passed_students)

{'Alex': 37, 'Kio': 85, 'Freebee': 57, 'Susan': 1, 'Dave': 96, 'Caroline': 60, 'Beth': 14, 'Freddie': 70}
37
85
57
1
96
60
14
70
{'Kio': 85, 'Freebee': 57, 'Dave': 96, 'Caroline': 60, 'Freddie': 70}

 

 

 

ex) 단어별 글자수를 딕셔너리 comprehension으로 나타내기

sentence = "What is the Airspeed Velocity of an Unladen Swallow?"
# Don't change code above ?
# Write your code below:
result = {word:len(word) for word in sentence.split()}
print(result)

{'What': 4, 'is': 2, 'the': 3, 'Airspeed': 8, 'Velocity': 8, 'of': 2, 'an': 2, 'Unladen': 7, 'Swallow?': 8}

 

 

 

ex) 섭씨 온도 데이터를 화씨로 변환

weather_c = {
    "Monday": 12,
    "Tuesday": 14,
    "Wednesday": 15,
    "Thursday": 14,
    "Friday": 21,
    "Saturday": 22,
    "Sunday": 24,
}
# ? Don't change code above ?
# Write your code ? below:
weather_f = {day:(temp*9/5+32) for (day,temp) in weather_c.items()}
print(weather_f)

{'Monday': 53.6, 'Tuesday': 57.2, 'Wednesday': 59.0, 'Thursday': 57.2, 'Friday': 69.8, 'Saturday': 71.6, 'Sunday': 75.2}

 

 

 

** pandas DataFrame에서의 Loop

 

#Looping through dictionaries:

student_dict = {
    "student": ["Kio", "James", "Lily"],
    "score": [95, 55, 99]
}
for (key, value) in student_dict.items():
    print(key)

 

student
score

 

    print(value)

['Kio', 'James', 'Lily']
[95, 55, 99]

 

 

 

student_dict = {
    "student": ["Kio", "James", "Lily"],
    "score": [95, 55, 99]
}
for (key, value) in student_dict.items():
    print(value)
print("\n")
import pandas
student_data_frame = pandas.DataFrame(student_dict)
print(student_data_frame)

['Kio', 'James', 'Lily']
[95, 55, 99]


  student  score
0     Kio     95
1   James     55
2    Lily     99

 

 

#Loop through a DataFrame

for (key, value) in student_data_frame.items():
    print(key)
    print(value)

student
0      Kio
1    James
2     Lily
Name: student, dtype: object
score
0    95
1    55
2    99
Name: score, dtype: int64

>>>>> output이 그닥 유용하게 사용될 것 같지 않음

 

 

#pandas의 iterrows()

#Loop through rows of a DataFrame

for (index, row) in student_data_frame.iterrows():
    print(index)

0
1
2

 

 

for (index, row) in student_data_frame.iterrows():
    print(row)

student    Kio
score       95
Name: 0, dtype: object
student    James
score         55
Name: 1, dtype: object
student    Lily
score        99
Name: 2, dtype: object

>> 특정 열 아래의 값을 구할 수 있다!!

 

for (index, row) in student_data_frame.iterrows():
    print(row.student)
for (index, row) in student_data_frame.iterrows():
    if row.student == "Kio":
        print(row.score)

Kio
James
Lily

95