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Use dict(zip(keys, values)) to make a dictionary from two lists whose items match by position. The first list supplies keys; the second supplies their values.
Build a dictionary from matching lists
Pair each key with the value at the same index, then pass those pairs to dict:
keys = ["name", "age"]
values = ["Ada", 36]
result = dict(zip(keys, values))
print(result)
# {'name': 'Ada', 36}zip(keys, values) produces pairs in order: ("name", "Ada") and ("age", 36). The dict constructor accepts an iterable of two-item key-value pairs and creates the mapping. See the Python documentation for zip and dictionary construction.
Choose what happens when list lengths differ
By default, zip stops as soon as the shorter input is exhausted. Any remaining items in the longer list are ignored, so a length mismatch can silently omit data.
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| What the mismatch means | Use | Behavior |
|---|---|---|
| A mismatch is an error | dict(zip(keys, values, strict=True)) |
Raises ValueError if the input lengths differ. The strict argument was added in Python 3.10. |
| Extra items should be ignored | dict(zip(keys, values)) |
Pairs items until the shorter input ends. |
| Missing items should be filled | itertools.zip_longest(keys, values) |
Pairs through the longer input and uses a fill value for missing items. Set an appropriate fillvalue if the default is not suitable. |
For example, to make unequal lengths fail rather than quietly discard items, use strict mode:
result = dict(zip(keys, values, strict=True))For padded pairs, choose the fill value explicitly and import zip_longest:
from itertools import zip_longest
result = dict(zip_longest(keys, values, fillvalue=None))With fillvalue=None, an unmatched key receives None, or an unmatched value is paired with the key None. Those entries may not be appropriate for your data; select a fill value that makes sense for how the resulting dictionary will be used. The Python built-in functions documentation describes both strict pairing and itertools.zip_longest.
Transform or filter pairs with a comprehension
Use a dictionary comprehension when you need to change values or omit certain pairs. It uses the same positional pairing and default shortest-list behavior as zip:
result = {
key: value.upper()
for key, value in zip(keys, values)
if isinstance(value, str)
}This example uppercases string values and skips values that are not strings. Add your own condition or transformation as needed; use strict=True in the zip call if unequal lengths should raise an error.
Account for duplicate keys
A dictionary can contain each key only once. If the key list repeats a key, the later paired value replaces the earlier one. For example, dict(zip(["color", "color"], ["blue", "green"])) produces {"color": "green"}. If every occurrence must be preserved, a dictionary is not the right representation unless you store multiple values under each key.
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