STSCI Python Introduction

Transcription

1 STSCI Python Introduction Class 5 Jim Hare Today s Agenda stpydb Module database interface module os Module commonly used methods os.path Module Manipulates pathnames shutil Module - High-level file operations Demonstration of Pmw Widgets Simple helloworld Tkinter program 1

2 Database Functions dbtools.py use with sql flat files. stpydb.py use to program queries and get results in variables to use in the module. stpydb Functions stpydb() - Connecting to the database. stpydb is a class object. getparammodechar - Returns the query param substitution char setparammodechar - Defines the query param substitution char setparam - Defines value for a named parameter execute - Executes the query returning one row at a time executeall - Executes the query returning all rows executeupdate - Executes an update/insert/delete query 2

3 stpydb Functions continued rowcount - Returns #rows affected by a query begintransaction - Starts a transaction on a given connection committransaction - Commits a transaction on a given connection rollbacktransaction - Aborts a transaction on a given connection clear - Clears an unfinished query stpydb Functions continued getdescription - Returns meta data info on last select query printdescription - Prints meta data report on last select query query - Pass a query string close - Shuts down the connection 3

4 stpydb Constructor Look at def init in /ess5/psdpython/stpydb.py, the constructor Examples: q1 = stpydb.stpydb() q2 = stpydb.stpydb('nomad') q3 = stpydb.stpydb(dbmsname='psttest4') q4 = stpydb.stpydb('nomad','psttest4') q5 = stpydb.stpydb(modulename='testpydb.py') q6 = stpydb.stpydb('r2d2','pstdev1','testpydb.py') Parameters, Queries and Execution - executeupdate Ex. Update from /ess5/psdpython/spssdb.py db= stpydb.stpydb(servername=server,dbmsname=database) param = [['PROP', proposal_id],['obset', obset_id], ['BEG',window_beg], ['END',window_end]] db.query('update qbwindows set window_beg ' 'window_end where proposal_id ' 'and obset_id db.setparam(param) db.executeupdate() return None 4

5 Parameters, Queries and Execution - execute Ex. Execute returns one record at a time param = ['sunit',suid[0]] db.query('select qs.proposal_id,qs.obset_id') db.query(' from qsbranching qs ') db.query('where qs.sunit_id db.setparam(param) result = {} while db.execute(result): obsetlist = obsetlist + \ ['%s:%s:01' % (result['proposal_id'],result['obset_id'])] Parameters, Queries and Execution - executeall Ex. executeall returns list of records currlist = [{}] q1.query("select d_scenar_acq, d_use_fgs_1, d_use_fgs_2, d_use_fgs_3 ") q1.query("from qbacqd_def") q1.executeall(currlist) for currdict in currlist: for field in currdict.keys(): print currdict[field] 5

6 Transactions q3.begintransaction() q3.query(querynew1) q3.executeupdate() q3.query(querynew2) q3.executeupdate() #NO error condition if you don't rollback! q3.rollbacktransaction() Tools and Examples spssdb.py functions related to spss database sirecon.py a tool to get 10.2 table data stpydb.py the tool developed for sybase interface testpydb.py tests developed to test stpydb 6

7 os Module Functions General Purpose Process Environment Files and Directories Process Management os.path - manipulates pathnames in a portable manner. General Purpose os Variables environ - mapping object of the current environment variables. linesep - \n for POSIX name - posix, nt, dos, mac, or os2 path - OS-dependent standard module for pathname operations 7

8 Process Environment os Functions Highlights chdir(path) - changes the current working dir to path getcwd() - gets the current working dir getpid() - get the process id of process getuid() - get the user id of current process putenv(varname, value) - Changes subprocess environment variable varname. uname() - returns (sysname,nodename,release,version,machine) File and Directory os Highlights chmod(path, mode) - changes access mode access(path,accessmode) - returns 1 if ok Accessmode - R_OK,W_OK,X_OK, or F_OK listdir(path) - List of filename returned mkdir(path, [mode]) - create directory mkdirs(path, [mode]) - makes directories to reach the leaf, recursive 8

9 Files and Directories os cont. remove(path) - remove the file path removedirs(path) - recursive removal rename(src, dst) - renames src to dst renames(old, new) - recursive rename rmdir(path) - removes the path Process Management os Functions Higlights exec l, le, lp, v, ve, vp, vpe - Many ways to execute a program path. fork() - creates a clone child process. spawn v,or ve (mode, path, args) (env) - spawns a program path in a new process system(command) - executes a system command in a subprocess 9

10 os.path Module Highlights abspath(path) - absolute full pathname abspath(../python/foo ) is /home/bz/python/foo basename(path) - returns the basename basename( /usr/local/python ) is python. dirname(path) - directory of the path dirname( /usr/local/python ) is /usr/local split(path) - returns tuple (dirname(),basename()) os.path Module Highlights cont. exists(path) - true if path exists isfile(path) - true if path is regular file isdir(path) - true if path is a directory join(path1,[,path2[, ]]) - intelligent join of one or mor paths join( /home, bz, Python ) is /home/bz/python splitext(path) - splitext( foo.txt ) is ( foo, txt ) 10

11 shutil Module Highlights copy(src, dst) - copies from src to dst and permissions. Other copys - copyfile, copymode, copystat, copy2 copytree(src, dst [, symlinks]) - recursively copies an entire directory tree. dst will be created and should not exist. Sylinks - true - symlinks same in the new tree; false - contents of linked files are copied to the new directory tree. rmtree(path, [, ignore_errors[, onerror]]) - remove directory tree Pmw Demo What s a Widget? 11

12 Tkinter helloworld Program A simple example of Tkinter 12