CODEWITHSUNDEEP
pythonstring
asterix
asterix

Reputation: 11

python substring is out of range

I am reading a message from serial. It is working fine.

If I use this code, it works 

while 1:
        data_raw=ser.read(33).decode('ascii')
        if len(data_raw) > 0:
                print(data_raw[0])

OUTPUT

===== RESTART: C:\Users\...=====
S
S
S
S
S

But if I use this code, it doesn't work

while 1:
        data_raw=ser.read(33).decode('ascii')
        if data_raw[0] is 'S':
                print(data_raw[0])

OUTPUT

    if data_raw[0] is 'S':
IndexError: string index out of range

Upvotes: 0

Views: 83

Answers (1)

amiabl
amiabl

Reputation: 1088

In the first case, you properly check the length of the data_raw list before accessing any item of it.

Whereas, in your second item you test a condition on the first item of data_raw if data_raw[0] is 'S': but you have to make sure this item is actually defined.

Here, Python tells you there is no data_raw[0]. You need to make sure len(data_raw) > 0 before accessing data_raw[0].

Upvotes: 2

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