Chapter 10: Problem 6

How can you determine whether a key-value pair exists in a dictionary?

Short Answer

Expert verified

Answer: You can determine whether a specific key-value pair exists in a Python dictionary by using the 'in' keyword to check if the key is present and then comparing the corresponding value to the known value. Here's an example: example_dict = {"apple": 5, "banana": 7, "orange": 3} key_to_check = "apple" value_to_check = 5 if key_to_check in example_dict: if example_dict[key_to_check] == value_to_check: print(f"The key-value pair ({key_to_check}, {value_to_check}) exists in the dictionary.") else: print(f"The key {key_to_check} exists, but with a different value.") else: print(f"The key {key_to_check} does not exist in the dictionary.")

Step by step solution

Understand Python dictionaries and key-value pairs

A dictionary is an unordered, mutable collection data type in Python that stores key-value pairs. Each key is unique and used as a reference to access the corresponding value. Here's an example: example_dict = {"apple": 5, "banana": 7, "orange": 3} In this example, "apple", "banana", and "orange" are the keys, and 5, 7, and 3 are the corresponding values.

Use the 'in' keyword to check if a key exists in the dictionary

The 'in' keyword is a membership operator that can be used to check if a specific key is present in the dictionary. The syntax is as follows: if key in dictionary: # Do something if the key is present else: # Do something if the key is not present

Implement the 'in' keyword to check for a key-value pair in a dictionary

To check if a specific key-value pair exists in the dictionary, first use the 'in' keyword to check if the key is present, and then compare the value with the known value. Here's an example: example_dict = {"apple": 5, "banana": 7, "orange": 3} key_to_check = "apple" value_to_check = 5 if key_to_check in example_dict: if example_dict[key_to_check] == value_to_check: print(f"The key-value pair ({key_to_check}, {value_to_check}) exists in the dictionary.") else: print(f"The key {key_to_check} exists, but with a different value.") else: print(f"The key {key_to_check} does not exist in the dictionary.")

Test the implementation with different examples

Test the implementation with different dictionaries, keys, and values to see if it correctly identifies whether a key-value pair exists. example_dict1 = {"apple": 5, "banana": 7, "orange": 3} key_to_check1, value_to_check1 = "apple", 5 example_dict2 = {"cat": 1, "dog": 2, "bird": 3} key_to_check2, value_to_check2 = "fish", 4 example_dict3 = {"John": 25, "Jane": 30, "Jim": 40} key_to_check3, value_to_check3 = "Jane", 30 Perform the same logic as in step 3 on each of these examples to check for the existence of the key-value pairs.

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How can you determine whether a key-value pair exists in a dictionary?

Short Answer

Step by step solution

Understand Python dictionaries and key-value pairs

Use the 'in' keyword to check if a key exists in the dictionary

Implement the 'in' keyword to check for a key-value pair in a dictionary

Test the implementation with different examples

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