python dictionary error when getting value from a given key -

i'm starting coding in python since yesterday , i'm going without problems. context program read rfid card , use readed tag associated username. work in embedded linux (debian gnu/linux 7 (wheezy)) on terra board. python version (python 2.7.3).

i create dictionary fill key/value pairs (both strings). when try value using 1 key exception don't understand.

def findtagbynumber(self, key):     global tags      value = ""     try:         print("all dictionary: " + str(self.tags))         print("get name key: " + str(key))         value = self.tags[key]         print("found name key: " + str(value))     except exception ex:         print("exception: " + str(ex))      return value 

the result this:

root@ariag25:/home/python# python main.py rfid::initialize rfid::get tag configurations rfid::serial port opened dictionary: {'4d0055ab3a': 'test1', '4d0055b6e4j': 'test2'} name key: 4d0055b6e4j exception: '\x024d0055b6e4j\x03' rfid::couldn't found tag 

can explain wrong code?

you still including rfid start , end flags; bytes hex values 02 , 03; these un-printable bytes not visible when print them directly. none of keys in dictionary include these bytes.

just printing key means don't see bytes, are there:

>>> key = '\x024d0055b6e4j\x03' >>> print key 4d0055b6e4j >>> key '\x024d0055b6e4j\x03' >>> print repr(key) '\x024d0055b6e4j\x03' 

the repr() function helps make bytes visual.

you strip bytes:

key.strip('\x02\x03') 

demo:

>>> key = '\x024d0055b6e4j\x03' >>> key.strip('\x02\x03') '4d0055b6e4j' >>> tags = {'4d0055ab3a': 'test1', '4d0055b6e4j': 'test2'} >>> key in tags false >>> key.strip('\x02\x03') in tags true 

another option add bytes dictionary keys instead:

{'\x024d0055ab3a\x03': 'test1', '\x024d0055b6e4j\x03': 'test2'}