Python - Tools/Utilities

The standard library comes with a number of modules that can be used both as modules and as command-line utilities.

Thedis Module

Thedis 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

import disdef 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

Thepdb 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 runpdb.py, set your path properly to Python lib directory. So let us trywith 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)

Theprofile 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 = 10varb = 20sum = vara + varbprint "vara + varb = %d" % sum

Now, try runningcProfile.py over this filesum.py as follow −

$cProfile.py sum.pyvara + varb = 30   4 function calls in 0.000 CPU seconds   Ordered by: standard namencalls   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 ......}

Thetabnanny 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 = 10varb = 20sum = vara + varbprint "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.