Use enumerate() with dict.items() to loop through a dictionary while keeping a position counter:
scores = {"Ada": 91, "Linus": 87, "Grace": 95}
for i, (name, score) in enumerate(scores.items()):
print(i, name, score)The counter starts at 0. It marks the entry’s position during iteration; it is not necessarily a key in scores.
Choose the loop based on what you need
Iterating over a dictionary directly produces its keys. Use .values() for values, .items() for key-value pairs, or enumerate() to add a separate counter.
| What you need | Loop |
|---|---|
| Keys only | for key in d: |
| Values only | for value in d.values(): |
| Keys and values | for key, value in d.items(): |
| Counter, keys, and values | for i, (key, value) in enumerate(d.items()): |
| Counter and keys only | for i, key in enumerate(d): |
The Python tutorial documents retrieving each key and its corresponding value with items(). The built-in enumerate() adds a counter to each item from an iterable.
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Use the counter for display, not as a key
A dictionary is a mapping, not a sequence indexed by position. In for i, (key, value) in enumerate(d.items()), i is generated by enumerate(), while key is the dictionary key. To retrieve the value, use d[key] rather than assuming d[i] refers to the entry at position i.
For a one-based counter, pass a starting value:
for i, (key, value) in enumerate(d.items(), start=1):
print(i, key, value)This changes the counter, not the dictionary’s keys. The official documentation describes the start argument as the value from which enumeration begins.
What determines dictionary iteration order?
In Python 3.7 and later, insertion order is guaranteed by the language: keys are produced in the order they were added. Replacing the value for an existing key does not change its position. Removing a key and inserting it again moves it to the end. CPython 3.6 also preserved insertion order, but only as an implementation detail, not a language guarantee. See the Python data model documentation.
Insertion order is not sorted order. If you specifically want keys in sorted order, iterate over sorted(d):
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for i, key in enumerate(sorted(d)):
print(i, key, d[key])This sorts the keys for the loop; it does not reorder the dictionary itself. The Python tutorial includes examples of sorting dictionary keys.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Select an entry by numeric position
d[0] looks up the key 0; it does not mean “the first entry.” If you need to select an entry by position, convert the entries to a list first:
entry = list(d.items())[i]
key, value = entryFor keys alone, list(d)[i] returns the key at that position in iteration order. These conversions create lists, so if your goal is simply to visit entries, iterate over the dictionary directly instead.
Quick Recap
Avoid common indexing and unpacking errors
- Using the counter as a key:
d[i]works only ifiis an actual key. Use the key yielded by the loop to access its value. - Unpacking the result of
items()incorrectly:enumerate(d.items())yields a counter and a key-value pair. Unpack it asfor i, (key, value) in .... - Expecting a missing key to behave like a position:
d[key]raisesKeyErrorif that key is absent. Used.get(key, default)when you want a fallback value, as shown in the Python tutorial. - Assuming insertion order in older Python versions: the language-level guarantee begins with Python 3.7; CPython 3.6’s ordering behavior was implementation-specific.
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