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Python - Tools/Utilities
The standard library comes with a number of modules that can be used both as modules and as command-line utilities.
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.
Example
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 −
3 0 LOAD_CONST 1 (10) 2 STORE_FAST 0 (vara) 4 4 LOAD_CONST 2 (20) 6 STORE_FAST 1 (varb) 6 8 LOAD_FAST 0 (vara) 10 LOAD_FAST 1 (varb) 12 BINARY_ADD 14 STORE_FAST 2 (sum) 7 16 LOAD_GLOBAL 0 (print) 18 LOAD_CONST 3 ('vara + varb = %d') 20 LOAD_FAST 2 (sum) 22 BINARY_MODULO 24 CALL_FUNCTION 1 26 POP_TOP 28 LOAD_CONST 0 (None) 30 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 −
vara = 10 varb = 20 sum = vara + varb print "vara + varb = %d" % sum
Now, try running cProfile.py over this file sum.py as follow −
$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 −
vara = 10 varb = 20 sum = vara + varb print "vara + varb = %d" % sum
If 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.