[Python] Unexpected Behavior in Spyder Debugger When Inspecting Variable Values Inside a while...

I'm debugging a while loop using pdb in Spyder and noticed a behavior that seems unexpected. Here's a simplified version of the code:

import pdb

idx = 0
pdb.set_trace()
while idx < 1:
print(str(idx))
idx = idx+1
print(str(idx))

pdb.set_trace()

• The first time the debugger stops at the first pdb.set_trace(), idx is displayed as 0 both in the Variable Explorer and in the Console - as expected.
• After continuing and hitting the second pdb.set_trace() inside the loop, idx appears to be still displayed as 0, even though it should have been incremented already.
• Trying to evaluate idx < 1 in the Console prints True, which is inconsistent with the expected state.
• Despite this, Spyder executes the loop correctly and exits the while loop after one iteration.

I tried to investigate this further, testing this other variation:

while idx < 2:
print(str(idx))
idx += 1
print(str(idx))

pdb.set_trace()


In this version, the value of idx is correctly updated in the Variable Explorer (and Console) only after the while condition is evaluated, and idx is finally displayed to be equal to 1 after pressing Ctrl+F10 (Debug current line). This makes it look like the Variable Explorer and Console are a step behind during debugging — even when the variable has technically already been updated.

My questions:

• Is this behavior normal or expected in Spyder's debugger, or is this a known issue?
• Am I misunderstanding how Spyder interacts with pdb or how the execution timeline should look?

The same issue occurs by manually putting breakpoints rather than using pdb, so it does not seem to be a pdb-specific problem. Any clarification would be appreciated.

I am running:

• Windows 10
• Spyder 6.0.7 (under conda 24.11.3)
• Python 3.12.7 64-bit
• Qt 5.15.2
• PyQt5 5.15.10

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