Use dict.items() to Iterate

ID

python.use_items_iterate_dict

Severity

info

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Best Practice

Language

Python

Tags

best-practice, code-style

Description

Reports for k in d: loops whose body indexes the same dict by the key (d[k]). The Python idiom is for k, v in d.items():, which avoids the per-iteration lookup and reads more clearly.

for key in mapping:
    value = mapping[key]              # FLAW
    do(key, value)

for key, value in mapping.items():    # OK
    do(key, value)

Rationale

d[k] does a hash lookup every iteration; d.items() yields the values directly. The performance difference is small but consistent, and the items() form is the canonical "I am iterating this dict" signal — readers do not have to check the body to know whether you wanted keys, values, or both.

Remediation

for key, value in mapping.items():
    process(key, value)

# When you only need the values:
for value in mapping.values():
    process(value)

References