The standard library comes with a number of modules that can be used both as modules and as command-line utilities.
You can run the disassembler from the command line. It compiles the given script and prints the disassembled byte codes to the STDOUT. You can also use dis as a module. The dis function takes a class, method, function or code object as its single argument.
You can run the debugger from the command line (type n [or next] to go to the next line and help to get a list of available commands) −
The dis Module:
The dis module is the Python disassembler. It converts byte codes to a format that is slightly more appropriate for human consumption.You can run the disassembler from the command line. It compiles the given script and prints the disassembled byte codes to the STDOUT. You can also use dis as a module. The dis function takes a class, method, function or code object as its single argument.
Example
#!/usr/bin/python import dis def sum(): vara = 10 varb = 20 sum = vara + varb print "vara + varb = %d" % sum # Call dis function for the function. dis.dis(sum)This would produce the following result −
6 0 LOAD_CONST 1 (10) 3 STORE_FAST 0 (vara) 7 6 LOAD_CONST 2 (20) 9 STORE_FAST 1 (varb) 9 12 LOAD_FAST 0 (vara) 15 LOAD_FAST 1 (varb) 18 BINARY_ADD 19 STORE_FAST 2 (sum) 10 22 LOAD_CONST 3 ('vara + varb = %d') 25 LOAD_FAST 2 (sum) 28 BINARY_MODULO 29 PRINT_ITEM 30 PRINT_NEWLINE 31 LOAD_CONST 0 (None) 34 RETURN_VALUE
The pdb Module
The pdb module is the standard Python debugger. It is based on the bdb debugger framework.You can run the debugger from the command line (type n [or next] to go to the next line and help to get a list of available commands) −
Example:
Before you try to run pdb.py, set your path properly to Python lib directory. So let us try with above example sum.py −$pdb.py sum.py > /test/sum.py(3)<module>() -> import dis (Pdb) n > /test/sum.py(5)<module>() -> def sum(): (Pdb) n >/test/sum.py(14)<module>() -> dis.dis(sum) (Pdb) n 6 0 LOAD_CONST 1 (10) 3 STORE_FAST 0 (vara) 7 6 LOAD_CONST 2 (20) 9 STORE_FAST 1 (varb) 9 12 LOAD_FAST 0 (vara) 15 LOAD_FAST 1 (varb) 18 BINARY_ADD 19 STORE_FAST 2 (sum) 10 22 LOAD_CONST 3 ('vara + varb = %d') 25 LOAD_FAST 2 (sum) 28 BINARY_MODULO 29 PRINT_ITEM 30 PRINT_NEWLINE 31 LOAD_CONST 0 (None) 34 RETURN_VALUE --Return-- > /test/sum.py(14)<module>()->None -v dis.dis(sum) (Pdb) n --Return-- > <string>(1)<module>()->None (Pdb)
The profile Module
The profile module is the standard Python profiler. You can run the profiler from the command line −Example
Let us try to profile the following program −#!/usr/bin/python vara = 10 varb = 20 sum = vara + varb print "vara + varb = %d" % sumNow, try running cProfile.py over this file sum.py as follows −
$cProfile.py sum.py vara + varb = 30 4 function calls in 0.000 CPU seconds Ordered by: standard name ncalls tottime percall cumtime percall filename:lineno 1 0.000 0.000 0.000 0.000 <string>:1(<module>) 1 0.000 0.000 0.000 0.000 sum.py:3(<module>) 1 0.000 0.000 0.000 0.000 {execfile} 1 0.000 0.000 0.000 0.000 {method ......}
The tabnanny Module
The tabnanny module checks Python source files for ambiguous indentation. If a file mixes tabs and spaces in a way that throws off indentation, no matter what tab size you're using, the nanny complains −Example
Let us try to profile the following program −#!/usr/bin/python vara = 10 varb = 20 sum = vara + varb print "vara + varb = %d" % sumIf you would try a correct file with tabnanny.py, then it won't complain as follows −
$tabnanny.py -v sum.py 'sum.py': Clean bill of health.
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