6.100L | Fall 2022 | Undergraduate

# Introduction to CS and Programming using Python

## Lecture 14: Dictionaries

Topics: Dictionaries: keys, values, mutability, iteration over a dict, examples

### Lecture Notes

Lecture 14: Dictionaries

Lecture 14 Code

Ch 5.7

### Finger Exercise Lecture 14

Question 1: Implement the function that meets the specifications below:

``````def keys_with_value(aDict, target):
"""
target: an integer or string
Assume that keys and values in aDict are integers or strings.
Returns a sorted list of the keys in aDict with the value target.
If aDict does not contain the value target, returns an empty list.
"""
# Your code here

# Examples:
aDict = {1:2, 2:4, 5:2}
target = 2
print(keys_with_value(aDict, target)) # prints the list [1,5]
``````

Question 2: Implement the function that meets the specifications below:

``````def all_positive(d):
"""
d is a dictionary that maps int:list
Suppose an element in d is a key k mapping to value v (a non-empty list).
Returns the sorted list of all k whose v elements sums up to a
positive value.
"""
# Your code here

# Examples:
d = {5:[2,-4], 2:[1,2,3], 1:[2]}
print(all_positive(d))   # prints the list [1, 2]
``````

6.100L Finger Exercises Lecture 14 Solutions

### Recitation 7

Recitations were smaller sections that reviewed the previous lectures. Files contain recitation notes and worked examples in code.

Recitation 7 Notes and Code

## Course Info

Fall 2022
##### Learning Resource Types
Lecture Videos
Lecture Notes
Problem Sets
Programming Assignments with Examples