Quirk of the import system

a.py

W = 1
print("a.py says: about to import b")
import b
print(f"a.py says: b imported with values {[name for name in dir(b) if '__' not in name]}")
X = 2

b.py

Y = 3
print("b.py says: about to import a")
import a
print(f"b.py says: a imported with values {[name for name in dir(a) if '__' not in name]}")
Z = 4

c.py

import a

results

C:\Users\Kevin\Desktop>a.py
a.py says: about to import b
b.py says: about to import a
a.py says: about to import b
a.py says: b imported with values ['Y']
b.py says: a imported with values ['W', 'X', 'b']
a.py says: b imported with values ['Y', 'Z', 'a']

C:\Users\Kevin\Desktop>c.py
a.py says: about to import b
b.py says: about to import a
b.py says: a imported with values ['W']
a.py says: b imported with values ['Y', 'Z', 'a']