do not modify a dictionary while iterating on it

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Metadata

ID: python-best-practices/collection-while-iterating

Language: Python

Severity: Error

Category: Error Prone

Description

Never update a dictionary while iterating on it. If you wish to update the dictionary, create a new dictionary from the existing values.

Non-Compliant Code Examples

i = 0
for element in my_list:
    my_list["stuff"] = i  # modifying a dictionary while iterating
    i += 1

Compliant Code Examples

i = 0
new_list = {}
for element in my_list:
    new_list["stuff"] = i  # putting value to a new dictionary
    i += 1

How to use this rule

1
2
rulesets:
  - python-best-practices     # Rules to enforce Python best practices.

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