Django values_list vs values

Strategic approach

Whether you reach for values or values_list depends on the data format you're after and the speed at which you want to retrieve it.

• values(): Provides a Queryable dictionary, enabling you to access data by its field name.
• values_list(): Offers a performance boost when the value is the sole focus, especially when generating distinct sets with set().

Know when to use each method

Going deep with values()

If you're not afraid to dig deep into your data, values() is your shovel:

• Flexibility: Lets you flex your coding muscles by accessing elements by key names; it's like a choose-your-own adventure book 📚.
• Data manipulation: You can do some pretty sweet Jiu-Jitsu MovesETs 🥋on dictionaries to manipulate data.

Going lean with values_list()

Care more about speed than detail? Then values_list() has got you covered:

• Performance: What it sacrifices in detail, it more than makes up for in speed; it's the Usain Bolt 🏃‍♂️ of data retrieval.
• Memory Usage: Less data-hungry which pays off with large datasets; it's more environmentally friendly 🌳... for your memory.

Double trouble with distinct()

To get unique records, give either method a sidekick called distinct():

• values('field').distinct(): Gets the attention of distinct dictionaries by 'field'.
• values_list('field', flat=True).distinct(): Calls out distinct values for a Listed school reunion 🏫.

Visualization

• values_list: A specific and precise list, just what you need, nothing more.

# Hand-picked list: '🍎', '🍌', '🍇'
shopping_list = Grocery.objects.values_list('produce', flat=True)
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• values: A detailed summary. It's like asking for the time and getting the history of the clock.

# detailed info: {'produce': '🍎', 'quantity': 5, 'notes': 'Get the ripe ones!'}
shopping_list = Grocery.objects.values('produce', 'quantity', 'notes')


Key point: values_list is your get-in, get-out option, while values is like having a backstage pass 🎫.

Things to watch out for

JSON output

If your target is JSON conversion, values() has a golden ticket 🎟️, since dictionaries convert to JSON cleanly. But never fear, values_list output can be converted into dictionaries with list comprehension, if needed.

Field type and transformations

• Single field focus: Use values_list('field', flat=True) when you're expecting a single-column output for an optimized performance.
• Transforming Data: With values, it's possible to apply annotations and functions to each field within the query-set. You can feel like a data magician 🧙‍♀️!

Pitfalls and Potentials

Be on alert for potential issues:

• Too many fields with flat=True: This one's a big no-no ⛔. values_list('id', 'name', flat=True) will return a TypeError. Only one field is allowed with flat=True.
• Unchangeable Tuples: Remember the one rule of tuple club: you can't change tuple club! Tuples are immutable, unlike dictionaries from values().

Playing around with sets and methods

Working with sets

Need to eliminate duplicates or intersect query-sets? Call set() to the rescue:

# Uniques only, please 🙅‍♂️
unique_values = set(MyModel.objects.values_list('field', flat=True))
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Chained methods

Both values and values_list love some good method chaining:

# Your wish is their command 🧞‍♀️
chained = MyModel.objects.values('field').filter(condition).order_by('field')
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