[Python](EN) Debug python code using pdb
Debug python code using pdb.
Environment and Prerequisite
- Linux base system
- Bash shell(/bin/bash)
- Python
pdb
What is pdb?
pdb: Interactive source code debugger for Python programs.
How to run
pdb run method - 1
- Run pdb in start time.
python3 -m pdb example.py
- Run example
$ python -m pdb test.py
> /Users/taewoo/test.py(1)<module>()
-> def test_sum(a,b):
(Pdb)
pdb run method - 2
- Add to code
# In python code
...
import pdb; pdb.set_trace()
...
- Run example
$ python test.py
> /Users/taewoo/test.py(6)<module>()
-> b=30
(Pdb)
Usage
Usage command list
l: Print codes of around current point. Current point will be marked by arrow.n: Move to next statement. In other words, run statement which is shown in abovelcommand’s arrow and move to next statement.s: Commonly used ‘Step Into’ command.--Call--will be shown after stepped in and--Return--will be shown after return.c: Run codes until meet next break point.r: Run command until meet return.w: Show current call stack.cl: Clear all break points.b: Make break point to file’s or package’s specific function or line.a: Print function’s all arguments.
Usage command example
l: Print codes of around current point. Current point will be marked by arrow.
(Pdb) l
1 def test_sum(a,b):
2 return a+b
3
4 a=10
5 -> b=30
6 c=test_sum(a,b)
7
8 for i in range(1,10):
9 a = a + i
10
11 import requests
n: Move to next statement. In other words, run statement which is shown in abovelcommand’s arrow and move to next statement.
(Pdb) n
> /Users/taewoo/test.py(6)<module>()
-> c=test_sum(a,b)
s: Commonly used ‘Step Into’ command.--Call--will be shown after stepped in and--Return--will be shown after return.
(Pdb) s
--Call--
> /Users/taewoo/test.py(1)test_sum()
-> def test_sum(a,b):
...
--Return--
> /Users/taewoo/test.py(5)test_sum()->40
-> return a+b
c: Run codes until meet next break point.
(Pdb) c
The program finished and will be restarted
r: Run command until meet return.
(Pdb) s
--Call--
> /Users/taewoo/test.py(1)test_sum()
-> def test_sum(a,b):
(Pdb) r
--Return--
> /Users/taewoo/test.py(5)test_sum()->40
-> return a+b
w: Show current call stack.
(Pdb) w
/Users/taewoo/.pyenv/versions/3.6.2/lib/python3.6/bdb.py(431)run()
-> exec(cmd, globals, locals)
<string>(1)<module>()
/Users/taewoo/test.py(9)<module>()
-> c=test_sum(a,b)
> /Users/taewoo/test.py(5)test_sum()->40
-> return a+b
cl: Clear all break points.
(Pdb) cl
Clear all breaks? y
b: Make break point to file’s or package’s specific function or line.
(Pdb) b 8
Breakpoint 1 at /Users/taewoo/test.py:8
(Pdb) b test_sum
Breakpoint 2 at /Users/taewoo/test.py:1
# Stop at line number 8
(Pdb) c
> /Users/taewoo/test.py(8)<module>()
-> b=30
# Stop at function
(Pdb) c
> /Users/taewoo/test.py(2)test_sum()
-> tmp=1
(Pdb) b
Num Type Disp Enb Where
1 breakpoint keep yes at /Users/taewoo/test.py:8
breakpoint already hit 2 times
2 breakpoint keep yes at /Users/taewoo/test.py:1
breakpoint already hit 1 time
a: Print function’s all arguments.
(Pdb) s
--Call--
> /Users/taewoo/test.py(1)test_sum()
-> def test_sum(a,b):
(Pdb) a
a = 10
b = 30
Others
- We can check value of variable using print function or just type it to pdb.
(Pdb) c
> /Users/taewoo/test.py(2)test_sum()
-> tmp=1
(Pdb) n
> /Users/taewoo/test.py(3)test_sum()
-> tmp=2
(Pdb) tmp
1
(Pdb) print(tmp)
1
(Pdb) type(data)
<class 'dict'>
(Pdb) data
{'data': [{'type': 'articles', 'id': '1', 'attributes': {'title': 'JSON API paints my bikeshed!', 'body': 'The shortest article. Ever.', 'created': '2015-05-22T14:56:29.000Z', 'updated': '2015-05-22T14:56:28.000Z'}, 'relationships': {'author': {'data': {'id': '42', 'type': 'people'}}}}], 'included': [{'type': 'people', 'id': '42', 'attributes': {'name': 'John', 'age': 80, 'gender': 'male'}}]}
- Add break point in code.
- Pdb will be stopped on
import pdb; pdb.set_trace()
def test_sum(a,b):
tmp=1
tmp=2
tmp=3
return a+b
a=10
b=30
c=test_sum(a,b)
for i in range(1,10):
a = a + i
import requests
import pdb; pdb.set_trace()
url = 'https://gist.githubusercontent.com/TWpower/771f9dfc8d9e1ddc0ecbdaea5b2e379e/raw/2c7785b4835138255bdadb71bd83702e53ac2677/test-example.json'
data = requests.get(url).json()
$ python -m pdb test.py
> /Users/taewoo/test.py(1)<module>()
-> def test_sum(a,b):
(Pdb) c
> /Users/taewoo/test.py(16)<module>()
-> url = 'https://gist.githubusercontent.com/TWpower/771f9dfc8d9e1ddc0ecbdaea5b2e379e/raw/2c7785b4835138255bdadb71bd83702e53ac2677/test-example.json'
(Pdb)