import gdb only works when your Python code is running within the GDB process. It’s not supposed to work from the regular system Python interpreter.

Explanation

• GDB embeds the Python interpreter so it can use Python as an extension language.
• You can’t just import gdb from /usr/bin/python like it’s an ordinary Python library because GDB isn’t structured as a library.
• What you can do is source MY-SCRIPT.py from within gdb (equivalent to running gdb -x MY-SCRIPT.py).

Example Program

Here’s a self contained example. Save the file below to t.py:

import gdb
gdb.execute('file /bin/cat')
o = gdb.execute('disassemble exit', to_string=True)
print(o)
gdb.execute('quit')

run:

$ gdb -q -x t.py 

and you’ll see the PLT stub for exit() disassembled. On x86-64 Linux:

Dump of assembler code for function exit@plt:
   0x0000000000401ae0 <+0>:  jmpq   *0x20971a(%rip)    # 0x60b200 <exit@got.plt>
   0x0000000000401ae6 <+6>:  pushq  $0x3d
   0x0000000000401aeb <+11>: jmpq   0x401700
End of assembler dump.

I’ve collected some resources on learning the GDB Python API here.