PYCHECKER(1) - man page online | user commands

Program to check python scripts for common mistakes.

Jan 2011
PYCHECKER(1)                              User Commands                              PYCHECKER(1)


pychecker - program to check python scripts for common mistakes


pychecker [options] files...


This manual page documents briefly the pychecker command. It was written for the Debian GNU/Linux distribution because the original program does not have a manual page. pychecker is a program that finds common bugs in python source code. It finds problems that are typically caught by a compiler for less dynamic languages, like C and C++. Because of the dynamic nature of python, some warnings may be incorrect; however, spurious warnings should be fairly infrequent. pychecker works in a combination of ways. First, it imports each module. If there is an import error, the module cannot be processed. The import provides some basic information about the module. The code for each function, class, and method is checked for possible problems.


By default, the /usr/bin/pychecker script executes pychecker using the default Python interpreter in /usr/bin/python. Some users may want to run pychecker with a different Python interpreter. To accommodate this, the /usr/bin/pychecker script supports the use of $PYTHONVER on the command-line, i.e. PYTHONVER=2.3 pychecker If $PYTHONVER is set, /usr/bin/pychecker will attempt to execute pychecker using /usr/bin/python$PYTHONVER instead of /usr/bin/python. Note, however, that this will only work for versions of the python interpreter supported by the current Debian Python infrastructure, not for any arbitrary Python interpreter installed in /usr/bin.


Long options can be preceded with no- to turn off (e.g., no-namedargs). Default settings are indicated by [brackets] Major Options: --only only warn about files passed on the command line [off] -e, --level the maximum error level of warnings to be displayed -#, --limit the maximum number of warnings to be displayed [10] -F, --config specify .pycheckrc file to use --quixote support Quixote's PTL modules --evil list of evil C extensions that crash the interpreter [[]] Error Control: -i, --import unused imports [on] -k, --pkgimport unused imports from [on] -M, --reimportself module imports itself [on] -X, --reimport reimporting a module [on] -x, --miximport module does import and from ... import [on] -l, --local unused local variables, except tuples [on] -t, --tuple all unused local variables, including tuples [off] -9, --members all unused class data members [off] -v, --var all unused module variables [off] -p, --privatevar unused private module variables [on] -g, --allglobals report each occurrence of global warnings [off] -n, --namedargs functions called with named arguments (like keywords) [off] -a, --initattr Attributes (members) must be defined in __init__() [off] -I, --initsubclass Subclass.__init__() not defined [off] -u, --callinit Baseclass.__init__() not called [on] -0, --abstract Subclass needs to override methods that only throw exceptions [on] -N, --initreturn Return None from __init__() [on] -8, --unreachable unreachable code [off] -2, --constCond a constant is used in a conditional statement [on] -1, --constant1 1 is used in a conditional statement (if 1: or while 1:) [off] --stringiter check if iterating over a string [on] --stringfind check improper use of string.find() [on] -A, --callattr Calling data members as functions [off] -y, --classattr class attribute does not exist [on] -S, --self First argument to methods [self] --classmethodargs First argument to classmethods [['cls', 'klass']] -T, --argsused unused method/function arguments [on] -z, --varargsused unused method/function variable arguments [on] -G, --selfused ignore if self is unused in methods [off] -o, --override check if overridden methods have the same signature [on] --special check if __special__ methods exist and have the correct signature [on] -U, --reuseattr check if function/class/method names are reused [on] -Y, --positive check if using unary positive (+) which is usually meaningless [on] -j, --moddefvalue check if modify (call method) on a parameter that has a default value [on] --changetypes check if variables are set to different types [off] --unpack check if unpacking a non-sequence [on] --unpacklen check if unpacking sequence with the wrong length [on] --badexcept check if raising or catching bad exceptions [on] -4, --noeffect check if statement appears to have no effect [on] --modulo1 check if using (expr % 1), it has no effect on integers and strings [on] --isliteral check if using (expr is const-literal), doesn't always work on integers and strings [on] Possible Errors: -r, --returnvalues check consistent return values [on] -C, --implicitreturns check if using implict and explicit return values [on] -O, --objattrs check that attributes of objects exist [on] -7, --slots various warnings about incorrect usage of __slots__ [on] -3, --properties using properties with classic classes [on] --emptyslots check if __slots__ is empty [on] -D, --intdivide check if using integer division [on] -w, --shadow check if local variable shadows a global [on] -s, --shadowbuiltin check if a variable shadows a builtin [on] Security: --input check if input() is used [on] -6, --exec check if the exec statement is used [off] Suppressions: -q, --stdlib ignore warnings from files under standard library [off] -b, --blacklist ignore warnings from the list of modules [['Tkinter', 'wxPython', 'gtk', 'GTK', 'GDK']] -Z, --varlist ignore global variables not used if name is one of these values [['__version__', '__warningregistry__', '__all__', '__credits__', '__test__', '__author__', '__email__', '__revision__', '__id__', '__copyright__', '__license__', '__date__']] -E, --unusednames ignore unused locals/arguments if name is one of these values [['_', 'empty', 'unused', 'dummy']] --deprecated ignore use of deprecated modules/functions [on] Complexity: -L, --maxlines maximum lines in a function [200] -B, --maxbranches maximum branches in a function [50] -R, --maxreturns maximum returns in a function [10] -J, --maxargs maximum # of arguments to a function [10] -K, --maxlocals maximum # of locals in a function [40] -5, --maxrefs maximum # of identifier references (Law of Demeter) [5] -m, --moduledoc no module doc strings [off] -c, --classdoc no class doc strings [off] -f, --funcdoc no function/method doc strings [off] Debug: --rcfile print a .pycheckrc file generated from command line args -P, --printparse print internal checker parse structures [off] -d, --debug turn on debugging for checker [off] -Q, --quiet turn off all output except warnings [off] -V, --version print the version of PyChecker and exit


Pychecker was written by Neal Norwitz and Eric C. Newton. Other contributors are listed in /usr/share/doc/pychecker/MAINTAINERS This manual page was written by Fredrik Steen <> for the Debian GNU/Linux system (but may be used by others). It has been subsequently modified by Kenneth J. Pronovici <>.


python(1) Running pychecker --help may provide more complete documentation of program options. The pychecker web page at <> contains some guidance on using the program.
pychecker 0.8.19 Jan 2011 PYCHECKER(1)
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pychecker(1) referred by
refer to python2.7(1)