Accessing a record's fields by name and by field index
Name:
Date:
Class:
A
Quick Questions
Shade in the A or B circle for each question.
1. A record is stored as a dictionary: student = {'name': 'Ava', 'year': 11}. Which line gets the student's name?
2. A record is stored as a list: student = ['Ava', 11, 'Red']. Which line gets the first field, 'Ava'?
3. Which statement about field indexes is true?
4. Given student = ('Ava', 11, 'Red'), which line gives an error?
5. Given student = {'name': 'Ava', 'year': 11}, which line is the better way to get the year?
B
Match the Pairs
Draw a line connecting each item on the left to its match on the right.
| Left column | Right column | |
|---|---|---|
| 1student['name'] | AGets the value of the field called name from a dictionary record | |
| 2student[0] | BIndex 3 is out of range. The record has 3 fields, so the valid indexes are 0, 1 and 2. Use student[2] for the last field. | |
| 3A tuple is an unchangeable record, so its fields can be read but not reassigned | Cname, age, year = student | |
| 4Unpacking copies each field of a record into its own variable in one line | Dstudent = ('Ava', 17, 'Year 12') | |
| 5student = ['Ava', 17, 'Year 12'] print(student[3]) | EThe field name is missing quotes, so Python looks for a variable called name. It should be student['name']. | |
| 6student = {'name': 'Ava', 'age': 17} print(student[name]) | FGets the first field of a list or tuple record by its field index |
C
Definitions
student['name']
D
Fill in the Blanks
Complete each line of code by filling in the missing parts.
1.
student = ['Ava', 7, 'Red']
print(student[_])
2.
student = ('Ava', 7, 'Red')
print(student[_])
3.
student = {'name': 'Ava', 'year': 7}
print(student['____'])
4.
student = ('Ava', 7, 'Red')
name, year, house = _______
print(name)
5.
student = {'name': 'Ava', 'year': 7}
print(_______['name'])
E
Spot the Error
Shade in the letter of the line that contains an error.
Question 1
A
s = {'name': 'Ava', 'yr': 9}
B
print(s[name])
C
print(s['yr'])
Question 2
A
student = ('Ava', 9, 'Red')
B
print(student[0])
C
print(student[3])
Question 3
A
student = ['Ava', 9, 'Red']
B
print(student['year'])
C
print(student[0])
Question 4
A
student = ('Ava', 9)
B
name = student[0]
C
student[1] = 10
D
print(name, year)
Question 5
A
student = ('Ava', 9, 'Red')
B
print(student[0])
C
name, year = student
D
print(name, house)
Answer Key
Accessing a record's fields by name and by field index
Section A: Quick Questions
Q1
B — student['name']
Q2
A — student[0]
Q3
B — The first field in a list or tuple record has index 0
Q4
A — student[1] = 12
Q5
A — student['year']
Section B: Match the Pairs
Q1
student['name'] → Gets the value of the field called name from a dictionary record
Q2
student[0] → Gets the first field of a list or tuple record by its field index
Q3
A tuple is an unchangeable record, so its fields can be read but not reassigned → student = ('Ava', 17, 'Year 12')
Q4
Unpacking copies each field of a record into its own variable in one line → name, age, year = student
Q5
student = ['Ava', 17, 'Year 12']
print(student[3]) → Index 3 is out of range. The record has 3 fields, so the valid indexes are 0, 1 and 2. Use student[2] for the last field.
Q6
student = {'name': 'Ava', 'age': 17}
print(student[name]) → The field name is missing quotes, so Python looks for a variable called name. It should be student['name'].
Section C: Definitions
Q1
student['name'] — Gets a field from a record by its field name. A list or tuple record uses the field index (its position) instead, such as student[0]. Indexes start at 0.Section D: Fill in the Blanks
Q1
student = ['Ava', 7, 'Red']
print(student[0])Q2
student = ('Ava', 7, 'Red')
print(student[2])Q3
student = {'name': 'Ava', 'year': 7}
print(student['year'])Q4
student = ('Ava', 7, 'Red')
name, year, house = student
print(name)Q5
student = {'name': 'Ava', 'year': 7}
print(student['name'])Section E: Spot the Error
Q1
B — A dictionary record's field name must be written as a string in quotes. Without quotes, Python looks for a variable called name and raises a NameError. It should be print(s['name']).
Q2
C — The tuple has 3 fields, so the field indexes are 0, 1 and 2. Index 3 is out of range and causes an IndexError. The house is at index 2: print(student[2]).
Q3
B — A list record has no field names, so you must use the field index (its position). The year is the second field, so it is student[1]. Using a string name on a list gives a TypeError.
Q4
C — A tuple is an unchangeable record, so you cannot assign a new value to one of its fields. This causes a TypeError. To read the field, use year = student[1].
Q5
C — When unpacking a record, the number of variables must match the number of fields. The tuple has 3 fields but only 2 variables are given, causing a ValueError. It should be name, year, house = student.