Python IF unexpected behavior when using OR

Question

I don't understand why the code below enters the IF statement.

#Cisco XR

print('*Read Channel before')
print(read_channel_password)

print(f'\nHostname: {hostname}')
print(f'Hostname upper: {hostname.upper()}')

if f':{hostname}#' or f':{hostname.upper()}#' in read_channel_password:
    print('\n*Read Channel after')
    print(read_channel_password)
    
    print("\nWhy are you here?")
    break

Console:

*Read Channel before

--- JUNOS 9.5R3.7 built 2009-10-28 16:48:40 UTC
{master}
user01@ed-ra1>

Hostname: ed-ra1
Hostname upper: ED-RA1

*Read Channel after

--- JUNOS 9.5R3.7 built 2009-10-28 16:48:40 UTC
{master}
user01@ed-ra1>

Why are you here?

When I change the IF to IF-ELIF instead of OR. It works normally. Am I missing something here?

in is not distributed across or. You need to write if x in variable or y in variable: — Barmar
– Barmar, Commented Feb 2, 2022 at 16:01

Eli Harold · Accepted Answer · 2022-02-02 16:09:24Z

3

Both sides of or need a conditional so instead of:

if f':{hostname}#' or f':{hostname.upper()}#' in read_channel_password:

You need:

if f':{hostname}#' in read_channel_password or f':{hostname.upper()}#' in read_channel_password:

Your current code will always return True as long as f':{hostname}#' is not empty since non-empty strings are truthy.

edited Feb 2, 2022 at 16:09

answered Feb 2, 2022 at 16:03

Eli Harold

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2 Comments

Daniel Walker Over a year ago

Exactly. If you do if f':{hostname}#', then you're just testing the boolean value of the string. Strings are considered to be true when they're not empty.

Pablo Over a year ago

Wow, basic stuff that I should know. Thank you guys.

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