Python's datetime Double Import Trap: 'type object datetime.datetime has no attribute datetime'

While adding code to a Flask API server, I suddenly hit this error:

AttributeError: type object 'datetime.datetime' has no attribute 'datetime'

My code looked like this:

datetime.datetime.now()

Nothing obviously wrong. But Python said "no such attribute."

What Was Happening

The real issue was at the top of the file:

import datetime
from datetime import datetime

These two lines coexist. Here's the problem:

• import datetime binds the module to the name datetime
• from datetime import datetime binds the class to the name datetime

The second import overwrites the first. Now datetime refers to the class, not the module.

When you call datetime.datetime.now(), Python looks for a datetime attribute on the datetime class — which doesn't exist. Hence the error.

Why It's Easy to Miss

When files grow long, you stop checking import lines. When copy-pasting code from other files, you bring imports along too. The collision stays hidden until runtime.

In my case: original code used import datetime; the code I added used from datetime import datetime. Both "correct" in isolation. Together: broken.

The Fix

Pick one style and stick with it.

Option A: module-style

import datetime

now = datetime.datetime.now()
delta = datetime.timedelta(days=7)

Option B: class-style

from datetime import datetime, timedelta

now = datetime.now()
delta = timedelta(days=7)

Do not mix.

Actual Patch

I chose Option B. Updated all occurrences of datetime.datetime.now() → datetime.now().

# Before
created_at = datetime.datetime.now().isoformat()
timestamp = datetime.datetime.now().strftime('%Y%m%d-%H%M%S')

# After
created_at = datetime.now().isoformat()
timestamp = datetime.now().strftime('%Y%m%d-%H%M%S')

3 locations. Fixed, Flask restarted, error gone.

Takeaway

Python's import is last-write-wins in the namespace. If you have multiple bindings to the same name, the last one wins — by design. Hard to spot in long files.

A linter or static analysis tool will usually warn about shadowed names. Adding these to CI/CD catches this class of bug before merge.

Most importantly: always review import lines when copy-pasting code between files.

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Symptom	Cause
datetime.datetime has no attribute datetime	from datetime import datetime overwrites import datetime
Fix	Standardize on one import style
Prevention	Linter / static analysis for import shadowing