1. Browsing Directories Copyright © Software Carpentry and The University of Edinburgh 2010-2011 This work is licensed under the Creative Commons Attribution License See http://software-carpentry.org/license.html for more information. Python

2. Browsing Directories We can use Python to

3. PythonBrowsing Directories We can use Python to –Save data to files

4. PythonBrowsing Directories We can use Python to –Save data to files –Read data from files

5. PythonBrowsing Directories We can use Python to –Save data to files –Read data from files But we might also want to

6. PythonBrowsing Directories We can use Python to –Save data to files –Read data from files But we might also want to –See what files we have

7. PythonBrowsing Directories We can use Python to –Save data to files –Read data from files But we might also want to –See what files we have –Delete files

8. PythonBrowsing Directories We can use Python to –Save data to files –Read data from files But we might also want to –See what files we have –Delete files –Group these into directories

9. PythonBrowsing Directories We can use Python to –Save data to files –Read data from files But we might also want to –See what files we have –Delete files –Group these into directories –Structure these directories into a tree

10. PythonBrowsing Directories We could use the shell

11. PythonBrowsing Directories We could use the shell Our program will be a mixture of –Python

12. PythonBrowsing Directories We could use the shell Our program will be a mixture of –Python –Shell commands

13. PythonBrowsing Directories We could use the shell Our program will be a mixture of –Python –Shell commands This is not portable

14. PythonBrowsing Directories We could use the shell Our program will be a mixture of –Python –Shell commands This is not portable Do it all in Python

15. PythonBrowsing Directories >>> from os import getcwd Import getcwd from the os module

16. PythonBrowsing Directories >>> from os import getcwd >>> getcwd()

17. PythonBrowsing Directories >>> from os import getcwd >>> getcwd() '/users/vlad' Current working directory

18. PythonBrowsing Directories >>> from os import getcwd >>> getcwd() '/users/vlad' >>> originaldir = getcwd() Save the current working directory in a variable

19. PythonBrowsing Directories >>> from os import getcwd >>> getcwd() '/users/vlad' >>> originaldir = getcwd() >>> print originaldir Use the variable

20. PythonBrowsing Directories >>> from os import getcwd >>> getcwd() '/users/vlad' >>> originaldir = getcwd() >>> print originaldir /users/vlad

21. PythonBrowsing Directories >>> from os import listdir

22. PythonBrowsing Directories >>> from os import listdir >>> listdir('.') vlad binmusicmail papers data solar notes.txt pizza.cfg solar.pdf swc

23. PythonBrowsing Directories >>> from os import listdir >>> listdir('.') vlad binmusicmail papers data solar notes.txt pizza.cfg solar.pdf swc Current working directory

24. PythonBrowsing Directories >>> from os import listdir >>> listdir('.') ['solar', 'mail', 'pizza.cfg', 'notes.txt', 'swc', 'data', 'papers', 'solar.pdf', 'bin', 'music'] vlad binmusicmail papers data solar notes.txt pizza.cfg solar.pdf swc

25. PythonBrowsing Directories >>> from os import listdir >>> listdir('.') ['solar', 'mail', 'pizza.cfg', 'notes.txt', 'swc', 'data', 'papers', 'solar.pdf', 'bin', 'music'] vlad binmusicmail papers data solar notes.txt pizza.cfg solar.pdf swc

26. PythonBrowsing Directories >>> listdir('.')

27. PythonBrowsing Directories >>> listdir(getcwd()) Use the result of getcwd as the input directory to listdir

28. PythonBrowsing Directories >>> listdir(getcwd()) ['solar', 'mail', 'pizza.cfg', 'notes.txt', 'swc', 'data', 'papers', 'solar.pdf', 'bin', 'music']

29. PythonBrowsing Directories >>> listdir(originaldir) Use a variable as the input directory to listdir

30. PythonBrowsing Directories >>> listdir(originaldir) ['solar', 'mail', 'pizza.cfg', 'notes.txt', 'swc', 'data', 'papers', 'solar.pdf', 'bin', 'music'] Use a variable as the input directory to listdir

31. PythonBrowsing Directories >>> listdir(originaldir) ['solar', 'mail', 'pizza.cfg', 'notes.txt', 'swc', 'data', 'papers', 'solar.pdf', 'bin', 'music'] >>> files = listdir(originaldir)

32. PythonBrowsing Directories >>> listdir(originaldir) ['solar', 'mail', 'pizza.cfg', 'notes.txt', 'swc', 'data', 'papers', 'solar.pdf', 'bin', 'music'] >>> files = listdir(originaldir) >>> print files

33. PythonBrowsing Directories >>> listdir(originaldir) ['solar', 'mail', 'pizza.cfg', 'notes.txt', 'swc', 'data', 'papers', 'solar.pdf', 'bin', 'music'] >>> files = listdir(originaldir) >>> print files ['solar', 'mail', 'pizza.cfg', 'notes.txt', 'swc', 'data', 'papers', 'solar.pdf', 'bin', 'music']

34. PythonBrowsing Directories >>> for file in files:Remember the colon

35. PythonBrowsing Directories >>> for file in files:... print file Remember the 4 spaces

36. PythonBrowsing Directories >>> for file in files:... print file... Remember RETURN to close the loop

37. PythonBrowsing Directories >>> for file in files:... print file... solar mail pizza.cfg notes.txt swc data papers solar.pdf bin music vlad binmusicmail papers data solar notes.txt pizza.cfg solar.pdf swc

38. PythonBrowsing Directories >>> getcwd() '/users/vlad' >>> from os import chdir

39. PythonBrowsing Directories >>> getcwd() '/users/vlad' >>> from os import chdir >>> chdir('data')

40. PythonBrowsing Directories >>> getcwd() '/users/vlad' >>> from os import chdir >>> chdir('data') >>> getcwd()

41. PythonBrowsing Directories >>> getcwd() '/users/vlad' >>> from os import chdir >>> chdir('data') >>> getcwd() '/users/vlad/data' chdir changes the current working directory

42. PythonBrowsing Directories >>> getcwd() '/users/vlad' >>> from os import chdir >>> chdir('data') >>> getcwd() '/users/vlad/data' >>> listdir(getcwd())

43. PythonBrowsing Directories >>> getcwd() '/users/vlad' >>> from os import chdir >>> chdir('data') >>> getcwd() '/users/vlad/data' >>> listdir(getcwd()) ['morse.txt', 'pdb', 'planets.txt', 'amino_acids.txt', 'elements', 'sunspot.txt']

44. PythonBrowsing Directories >>> getcwd() '/users/vlad' >>> from os import chdir >>> chdir('data') >>> getcwd() '/users/vlad/data' >>> listdir(getcwd()) ['morse.txt', 'pdb', 'planets.txt', 'amino_acids.txt', 'elements', 'sunspot.txt'] >>> chdir(originaldir)

45. PythonBrowsing Directories >>> getcwd() '/users/vlad' >>> from os import chdir >>> chdir('data') >>> getcwd() '/users/vlad/data' >>> listdir(getcwd()) ['morse.txt', 'pdb', 'planets.txt', 'amino_acids.txt', 'elements', 'sunspot.txt'] >>> chdir(originaldir) >>> getcwd()

46. PythonBrowsing Directories >>> getcwd() '/users/vlad' >>> from os import chdir >>> chdir('data') >>> getcwd() '/users/vlad/data' >>> listdir(getcwd()) ['morse.txt', 'pdb', 'planets.txt', 'amino_acids.txt', 'elements', 'sunspot.txt'] >>> chdir(originaldir) >>> getcwd() '/users/vlad'

47. PythonBrowsing Directories >>> chdir('data') bindatauserstmp / root imhoteplarryvlad data

48. PythonBrowsing Directories >>> chdir('data') >>> getcwd() bindatauserstmp / root imhoteplarryvlad data

49. PythonBrowsing Directories >>> chdir('data') >>> getcwd() '/users/vlad/data' bindatauserstmp / root imhoteplarryvlad data What Python considers to be the current working directory

50. PythonBrowsing Directories >>> chdir('data') >>> getcwd() '/users/vlad/data' >>> CTRL-D bindatauserstmp / root imhoteplarryvlad data What Python considers to be the current working directory

51. PythonBrowsing Directories >>> chdir('data') >>> getcwd() '/users/vlad/data' >>> CTRL-D $ pwd bindatauserstmp / root imhoteplarryvlad data What Python considers to be the current working directory

52. PythonBrowsing Directories >>> chdir('data') >>> getcwd() '/users/vlad/data' >>> CTRL-D $ pwd '/users/vlad' bindatauserstmp / root imhoteplarryvlad data What Python considers to be the current working directory What the shell considers to be the current working directory

53. PythonBrowsing Directories os Miscellaneous operating system interfaces getcwd Get current working directory listdir List directory contents chdirChange directory

54. May 2011 created by Mike Jackson and Greg Wilson Copyright © Software Carpentry and The University of Edinburgh 2010-2011 This work is licensed under the Creative Commons Attribution License See http://software-carpentry.org/license.html for more information.