class Foo(object):
    # self is not used, the method does not need
    # to be bound, it should be declared static
    def bar(self, a, b, c):
        return a + b - c

class Foo(object):
    @staticmethod
    def bar(a, b, c):
        return a + b - c

• Iterate over all the statement node of the AST
• Check that the statement is a class definition (ast.ClassDef)
• Iterate over all the function definitions (ast.FunctionDef) of that class statement to check if it is already declared with @staticmethod or not
• If the method is not declared static, we need to check if the first argument (self) is used somewhere in the method

[entry_points]
flake8.extension =
    [ ]
    H904 = hacking.checks.other:StaticmethodChecker
    H905 = hacking.checks.other:StaticmethodChecker

@core.flake8ext
class StaticmethodChecker(object):
    def __init__(self, tree, filename):
        self.tree = tree
 
    def run(self):
        pass

@core.flake8ext
class StaticmethodChecker(object):
    def __init__(self, tree, filename):
        self.tree = tree
 
    def run(self):
        for stmt in ast.walk(self.tree):
            # Ignore non-class
            if not isinstance(stmt, ast.ClassDef):
                continue

for stmt in ast.walk(self.tree):
    # Ignore non-class
    if not isinstance(stmt, ast.ClassDef):
        continue
    # If it's a class, iterate over its body member to find methods
    for body_item in stmt.body:
        # Not a method, skip
        if not isinstance(body_item, ast.FunctionDef):
            continue

for stmt in ast.walk(self.tree):
    # Ignore non-class
    if not isinstance(stmt, ast.ClassDef):
        continue
    # If it's a class, iterate over its body member to find methods
    for body_item in stmt.body:
        # Not a method, skip
        if not isinstance(body_item, ast.FunctionDef):
            continue
        # Check that it has a decorator
        for decorator in body_item.decorator_list:
            if (isinstance(decorator, ast.Name)
               and decorator.id == 'staticmethod'):
                # It's a static function, it's OK
                break
        else:
            # Function is not static, we do nothing for now
            pass

for stmt in ast.walk(self.tree):
    # Ignore non-class
    if not isinstance(stmt, ast.ClassDef):
        continue
    # If it's a class, iterate over its body member to find methods
    for body_item in stmt.body:
        # Not a method, skip
        if not isinstance(body_item, ast.FunctionDef):
            continue
        # Check that it has a decorator
        for decorator in body_item.decorator_list:
            if (isinstance(decorator, ast.Name)
               and decorator.id == 'staticmethod'):
                # It's a static function, it's OK
                break
        else:
            try:
                first_arg = body_item.args.args[0]
            except IndexError:
                yield (
                    body_item.lineno,
                    body_item.col_offset,
                    "H905: method misses first argument",
                    "H905",
                )
                # Check next method
                continue

for stmt in ast.walk(self.tree):
    # Ignore non-class
    if not isinstance(stmt, ast.ClassDef):
        continue
    # If it's a class, iterate over its body member to find methods
    for body_item in stmt.body:
        # Not a method, skip
        if not isinstance(body_item, ast.FunctionDef):
            continue
        # Check that it has a decorator
        for decorator in body_item.decorator_list:
            if (isinstance(decorator, ast.Name)
               and decorator.id == 'staticmethod'):
                # It's a static function, it's OK
                break
        else:
            try:
                first_arg = body_item.args.args[0]
            except IndexError:
                yield (
                    body_item.lineno,
                    body_item.col_offset,
                    "H905: method misses first argument",
                    "H905",
                )
                # Check next method
                continue
            for func_stmt in ast.walk(body_item):
                if six.PY3:
                    if (isinstance(func_stmt, ast.Name)
                       and first_arg.arg == func_stmt.id):
                        # The first argument is used, it's OK
                        break
                else:
                    if (func_stmt != first_arg
                       and isinstance(func_stmt, ast.Name)
                       and func_stmt.id == first_arg.id):
                        # The first argument is used, it's OK
                        break
            else:
                yield (
                    body_item.lineno,
                    body_item.col_offset,
                    "H904: method should be declared static",
                    "H904",
                )

The Hacker's Guide to Python

A book I wrote talking about designing Python applications, state of the art, advice to apply when building your application, various Python tips, etc. Interested? Check it out.

Why Johnny Doesn t Read When someone needs to know something, they might go look for some documentation, or they might ask someone else or just guess wildly. The behaviour look for documentation is often reinforced negatively, by the result documentation doesn t exist . At the same time, the behaviours ask someone and guess wildly are positively reinforced, by the results I get my question answered and/or at least I can get on with my work . Over time, people optimise their behaviour by skipping the look for documentation step, and just go straight to asking other people (or guessing wildly).

Why Johnny Doesn t Write When someone writes documentation, they re hoping that people will read it and not have to ask them questions in order to be productive and do the right thing. Hence, the behaviour write documentation is negatively reinforced by the results I still get asked questions , and nobody does things the right way around here, dammit! Worse, though, is that there is very little positive reinforcement for the author: when someone does read the docs, and thus doesn t ask a question, the author almost certainly doesn t know they dodged a bullet. Similarly, when someone does things the right way, it s unlikely that anyone will notice. It s only the mistakes that catch the attention. Given that the experience of writing documentation tends to skew towards the negative, it s not surprising that eventually, the time spent writing documentation is reallocated to other, more utility-producing activities.

Death Spiral The combination of these two situations is self-reinforcing. While a suitably motivated reader might start by strictly looking for documentation, or an author initially be enthused to always fully documenting their work, over time the reflex will be for readers to just go ask someone, because there s never any documentation! , and for authors to not write documentation because nobody bothers to read what I write anyway! . It is important to recognise that this iterative feedback loop is the natural state of the reader/author ecosystem, resulting in something akin to thermodynamic entropy. To avoid the system descending into chaos, energy needs to be constantly applied to keep the system in order.

The Solution Effective methods for avoiding the vicious circle can be derived from the things that cause it. Change the forces that apply themselves to readers and authors, and they will behave differently. On the reader s side, the most effective way to encourage people to read documentation is for it to consistently exist. This means that those in control of a project or system mustn t consider something done until the documentation is in a good state. Patches shouldn t be landed, and releases shouldn t be made, unless the documentation is altered to match the functional changes being made. Yes, this requires discipline, which is just a form of energy application to prevent entropic decay. Writing documentation should be an explicit and well-understood part of somebody s job description. Whoever is responsible for documentation needs to be given the time to do it properly. Writing well takes time and mental energy, and that time needs to be factored into the plans. Never forget that skimping on documentation, like short-changing QA or customer support, is a false economy that will cost more in the long term than it saves in the short term. Even if the documentation exists, though, some people are going to tend towards asking people rather than consulting the documentation. This isn t a moral failing on their part, but only happens when they believe that asking someone is more beneficial to them than going to the documentation. To change the behaviour, you need to change the belief. You could change the belief by increasing the cost of asking. You could fire (or hellban) anyone who ever asks a question that is answered in the documentation. But you shouldn t. You could yell RTFM! at everyone who asks a question. Thankfully that s one acronym that s falling out of favour. Alternately, you can reduce the cost of getting the answer from the documentation. Possibly the largest single productivity boost for programmers, for example, has been the existence of Google. Whatever your problem, there s a pretty good chance that a search or two will find a solution. For your private documentation, you probably don t have the power of Google available, but decent full-text search systems are available. Use them. Finally, authors would benefit from more positive reinforcement. If you find good documentation, let the author know! It requires a lot of effort (comparatively) to look up an author s contact details and send them a nice e-mail. The like button is a more low-energy way of achieving a similar outcome you click the button, and the author gets a warm, fuzzy feeling. If your internal documentation system doesn t have some way to close the loop and let readers easily give authors a bit of kudos, fix it so it does. Heck, even if authors just know that a page they wrote was loaded N times in the past week, that s better than the current situation, in which deafening silence persists, punctuated by the occasional plaintive cry of Hey, do you know how to ? . Do you have any other ideas for how to encourage readers to read, and for authors to write?

% ?_isa 

$ rpm -qRp net-snmp-devel-5.7.2-18.el6.x86_64.rpm grep perl
perl-devel(x86-64)

$ rpm -qRp net-snmp-devel-5.7.2-19.el5.centos.x86_64.rpm  grep perl
perl

yum install net-snmp-devel.x86_64

• Christopher writes that on Fedora, annoying, niggling problems that used to be straightforward to isolate, diagnose and resolve by virtue of the platform s simple, logical architecture have morphed into a morass that s worse than the Windows Registry. Alessandro Perucchi adds that he s been using Linux for decades, and now his wifi doesn t work, suspend doesn t work, etc. in Fedora and he is surprisingly unable to fix it himself.
• Nate bargman writes, in a really insightful comment, I do feel like as though I m becoming less a master of and more of a slave to the computing software I use. This is not a good thing.
• Singh makes the valid point that this stuff is in such a state of flux that even if a person is one of the few dozen in the world that understand what goes into a session today, the knowledge will be outdated in 6 months. (Hal, anyone?)

Changes in version 0.2.0 (2015-02-07)

• Added support for Pushbullet 'channels' (once again thanks to Mike Birdgeneau for the initial push on this)
• Support for pushes was solidified: proper choices of either device, email or channel should work in all cases
• S3 methods are now properly exports (thanks to Henrik Bengtsson)
• File transfer mode has been improved / corrected (thanks to Mike Birdgeneau)
• The regression test suite was expanded and robustified
• This NEWS file was added. Better late than never.

This post by Dirk Eddelbuettel originated on his Thinking inside the box blog. Please report excessive re-aggregation in third-party for-profit settings.

( ) a crazy story about Mel nearly dying in a crash on Dead Man s Curve on Hollywood Boulevard and about the moment two weeks later when Bugs Bunny emerged from Mel s coma before Mel did. In fact, according to neurosurgeon Louis Conway who attended to Mel at the time, it seemed as though Bugs Bunny was trying to save his life.

But imagine an alternate timeline for the Columbia mission in which NASA quickly realized just how devastating the foam strike had been. Could the Columbia astronauts have been safely retrieved from orbit?

En El Chavo del Ocho, Bola os, o el Camus azteca, cre su propia versi n del mito de S sifo. El chavo y compa a est n condenados a empujar por una empinada colina todos los d as esta piedra enorme que siempre regresa, obligandolos al tormento del eterno retorno. La piedra de Quico es cuadrada, no rueda, se desliza. Es c mico, a pesar de tr gico.

• CC1200 radio chip is about 5dB more sensitive than TeleDongle's CC1111.
• LPC11U14 CPU can be reprogrammed over the USB link.

• Make sure the startup flight computer beeps are consistent. Sometimes, it was taking long enough to beep out the battery voltage that the flight computer state was changing in the middle, causing a bit of confusion.
• Change TeleDongle's LED indicators during telemetry reception. The green LED blinks on successful packet reception, and the red LED blinks when a packet with an invalid checksum is received.
• The SPI driver used in both TeleDongle v3 and TeleGPS has been rewritten to avoid locking up under heavy CPU load. If you've got a TeleGPS board, you'll want to reflash with new firmware.

• AltosUI can now compute and display tilt angle when graphing eeprom log data from TeleMega and EasyMega.
• The AltosUI tool window is shown when starting with a data file. This way, when you double-click on a file in the file manager, you'll get the whole AltosUI interface, rather than just the graphing window.
• At the end of replaying an old log file, stick 'done' in the Age field so you can tell the recording is over.

• Use a different Windows API to discover USB device ids. This works better on my new HP Windows 7 machine. Maybe it will work better for other people too?
• Look in more places in the Windows registry to try and find the installed Java version. It appears that the default Java download from Oracle is a 32-bit version? In any case, that version sticks its install information in a different spot in the registry.
• Fix file associations on Windows when Java isn't installed in the system root.
• Make 'Scan Channels' work better with new AltOS firmware which only reports device configuration information once ever five seconds.

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21  
22  

$ grep LOGIN /var/log/syslog.1  
   grep FAILED.*201.163.94.42 
   awk ' print $7 " " $8 ' 
   sort uniq -c

library(drat)
addRepo("eddelbuettel")

drat:::add("eddelbuettel")

library(drat)
insertPackage("foo_0.1.0.tar.gz")

drat:::insert("foo_0.1.0.tar.gz", "/opt/myWork/git")

This post by Dirk Eddelbuettel originated on his Thinking inside the box blog. Please report excessive re-aggregation in third-party for-profit settings.

$ hash -d -- -lldpd=/home/bernat/code/deezer/lldpd
$ echo ~-lldpd/README.md
/home/bernat/code/deezer/lldpd/README.md
$ head -n1 ~-lldpd/README.md
lldpd: implementation of IEEE 802.1ab (LLDP)

for link ($MARKPATH/*(N@))  
    hash -d -- -$ link:t =$ link:A 
 

$ pwd
/home/bernat/code/deezer/lldpd/src/lib
$ echo $ (%):-%~ 
~-lldpd/src/lib

bookmark()  
    if (( $# == 0 )); then
        # When no arguments are provided, just display existing
        # bookmarks
        for link in $MARKPATH/*(N@); do
            local markname="$fg[green]$ link:t $reset_color"
            local markpath="$fg[blue]$ link:A $reset_color"
            printf "%-30s -> %s\n" $markname $markpath
        done
    else
        # Otherwise, we may want to add a bookmark or delete an
        # existing one.
        local -a delete
        zparseopts -D d=delete
        if (( $+delete[1] )); then
            # With  -d , we delete an existing bookmark
            command rm $MARKPATH/$1
        else
            # Otherwise, add a bookmark to the current
            # directory. The first argument is the bookmark
            # name.  .  is special and means the bookmark should
            # be named after the current directory.
            local name=$1
            [ $name == "." ] && name=$ PWD:t 
            ln -s $PWD $MARKPATH/$name
        fi
    fi
 

Dynamic named directories Another (more complex) way to achieve the same thing is using dynamic named directories. I was initially using this solution but it is far more complex. This section is only here for historical reason. You can find the complete implementation in my GitHub repository. During file name expansion, a ~ followed by a string in square brackets is provided to the zsh_directory_name() function which will eventually reply with a directory name. This feature can be used to implement directory bookmarks:

$ cd ~[@lldpd]
$ pwd
/home/bernat/code/deezer/lldpd
$ echo ~[@lldpd]/README.md
/home/bernat/code/deezer/lldpd/README.md
$ head -n1 ~[@lldpd]/README.md
lldpd: implementation of IEEE 802.1ab (LLDP)

Like for static named directories, because ~[@lldpd] is substituted during file name expansion, it is possible to use it in any command like a regular directory.

Basic implementation Bookmarks are still kept into a dedicated directory, $MARKPATH and are still symbolic links. Here is how the core feature is implemented:

_bookmark_directory_name()  
    emulate -L zsh #  
    setopt extendedglob
    case $1 in
        n)
            [ [ $2 != ( #b)"@"(?*) ]] && return 1 #  
            typeset -ga reply
            reply=($ $ :-$MARKPATH/$match[1] :A ) #  
            return 0
            ;;
        *)
            return 1
            ;;
    esac
    return 0
 
add-zsh-hook zsh_directory_name _bookmark_directory_name

zsh_directory_name() is a function accepting hooks²: instead of defining it directly, we define another function and register it as a hook with add-zsh-hook. The hook is expected to handle different situations. The first one is to be able to transform a dynamic name into a regular directory name. In this case, the first parameter of the function is n and the second one is the dynamic name. In , the call to emulate will restore the pristine behaviour of Zsh and also ensure that any option set in the scope of the function will not have an impact outside. The function can then be reused safely in another environment. In , we check that the dynamic name starts with @ followed by at least one character. Otherwise, we declare we don t know how to handle it. Another hook will get the chance to do something. (#b) is a globbing flag. It activates backreferences for parenthesised groups. When a match is found, it is stored as an array, $match. In , we build the reply. We could have just returned $MARKPATH/$match[1] but to hide the symbolic link mechanism, we use the A modifier to ask Zsh to resolve symbolic links if possible. Zsh allows nested substitutions. It is therefore possible to use modifiers and flags on anything. $ :-$MARKPATH/$match[1] is a common trick to turn $MARKPATH/$match[1] into a parameter substitution and be able to apply the A modifier on it.

Completion Zsh is also able to ask for completion of a dynamic directory name. In this case, the completion system calls the hook function with c as the first argument.

_bookmark_directory_name()  
    # [...]
    case $1 in
        c)
            # Completion
            local expl
            local -a dirs
            dirs=($MARKPATH/*(N@:t)) #  
            dirs=("@"$ ^dirs ) #  
            _wanted dynamic-dirs expl 'bookmarked directory' compadd -S\] -a dirs
            return
            ;;
        # [...]
    esac
    # [...]
 

First, in , we create a list of possible bookmarks. In *(N@:t), N@ is a glob qualifier. N allows us to not return nothing if there is no match (otherwise, we would get an error) while @ only returns symbolic links. t is a modifier which will remove all leading pathname components. This is equivalent to use basename or $ something##*/ in POSIX shells but it plays nice with glob expressions. In , we just add @ before each bookmark name. If we have b1, b2 and b3 as bookmarks, $ ^dirs expands to b1,b2,b3 and therefore "@"$ ^dirs expands to the (@b1 @b2 @b3) array. The result is then feeded into the completion system.

Prompt expansion Many people put the name of the current directory in their prompt. It would be nice to have the bookmark name instead of the full name when we are below a bookmarked directory. That s also possible!

$ pwd
/home/bernat/code/deezer/lldpd/src/lib
$ echo $ (%):-%~ 
~[@lldpd]/src/lib

The prompt expansion system calls the hook function with d as first argument and the file name to transform.

_bookmark_directory_name()  
    # [...]
    case $1 in
        d)
            local link slink
            local -A links
            for link ($MARKPATH/*(N@))  
                links[$  #link:A $'\0'$ link:A ]=$ link:t  #  
             
            for slink ($ (@On)$ (k)links )  
                link=$ slink#*$'\0'  #  
                if [ [ $2 = ( #b)($ link )( /*) ]]; then
                    typeset -ga reply
                    reply=("@"$ links[$slink]  $(( $  #match[1]  )) )
                    return 0
                fi
             
            return 1
            ;;
        # [...]
    esac
    # [...]
 

OK. This is some black Zsh wizardry. Feel free to skip the explanation. This is a bit complex because we want to substitute the most specific bookmark, hence the need to sort bookmarks by their target lengths. In , the associative array $links is created by iterating on each symbolic link ($link) in the $MARKPATH directory. The goal is to map a target directory with the matching bookmark name. However, we need to iterate on this map from the longest to the shortest key. To achieve that, we prepend each key with its length. Remember, $ link:A is the absolute path with symbolic links resolved. So, $ #link:A is the length of this path. We concatenate the length of the target directory with the target directory name and use $'\0' as a separator because this is the only safe character for this purpose. The result is mapped to the bookmark name. The second loop is an iteration on the keys of the associative array $links (thanks to the use of the k parameter flag in $ (k)links ). Those keys are turned into an array (@ parameter flag) and sorted numerically in descending order (On parameter flag). Since the keys are directory names prefixed by their lengths, the first match will be the longest one. In , we extract the directory name from the key by removing the length and the null character at the beginning. Then, we check if the extracted directory name matches the file name we have been provided. Again, (#b) just activates backreferences. With extended globbing, we can use the or operator, . So, when either the file name matches exactly the directory name or is somewhere deeper, we create the reply which is an array whose first member is the bookmark name and the second member is the untranslated part of the file name.

Easy typing Typing ~[@ is cumbersome. Hopefully, Zsh line editor can be extended with additional bindings. The following snippet will substitute @@ (if typed without a pause) by ~[@:

vbe-insert-bookmark()  
    emulate -L zsh
    LBUFFER=$ LBUFFER "~[@"
 
zle -N vbe-insert-bookmark
bindkey '@@' vbe-insert-bookmark

In combination with the autocd option and completion, it is quite easy to jump to a bookmarked directory.

---

1. For example:

   $ lldpd=/home/bernat/code/deezer/lldpd
   $ echo $lldpd/README.md
   /home/bernat/code/deezer/lldpd/README.md
   $ head -n1 $lldpd/README.md
   lldpd: implementation of IEEE 802.1ab (LLDP)
   

   The drawback is that you don t have a separate namespace for your bookmarks. You can still use a special prefix for that. Also, no prompt expansion.
2. Other functions accepting hooks are chpwd() or precmd().

# Automatically added by dh_installinit
if [ -x "/etc/init.d/keystone" ]; then
update-rc.d keystone defaults >/dev/null
fi
if [ -x "/etc/init.d/keystone" ]   [ -e "/etc/init/keystone.conf" ]; then
invoke-rc.d keystone start   true
fi
# End automatically added section
# Automatically added by dh_systemd_enable
# This will only remove masks created by d-s-h on package removal.
deb-systemd-helper unmask keystone.service >/dev/null   true
# was-enabled defaults to true, so new installations run enable.
if deb-systemd-helper --quiet was-enabled keystone.service; then
# Enables the unit on first installation, creates new
# symlinks on upgrades if the unit file has changed.
deb-systemd-helper enable keystone.service >/dev/null   true
else
# Update the statefile to add new symlinks (if any), which need to be
# cleaned up on purge. Also remove old symlinks.
deb-systemd-helper update-state keystone.service >/dev/null   true
fi
# End automatically added section

# Automatically added by dh_systemd_enable
# This will only remove masks created by d-s-h on package removal.
deb-systemd-helper unmask keystone.service >/dev/null   true
# was-enabled defaults to true, so new installations run enable.
if deb-systemd-helper --quiet was-enabled keystone.service; then
# Enables the unit on first installation, creates new
# symlinks on upgrades if the unit file has changed.
deb-systemd-helper enable keystone.service >/dev/null   true
else
# Update the statefile to add new symlinks (if any), which need to be
# cleaned up on purge. Also remove old symlinks.
deb-systemd-helper update-state keystone.service >/dev/null   true
fi
# End automatically added section
# Automatically added by dh_installinit
if [ -x "/etc/init.d/keystone" ]; then
update-rc.d keystone defaults >/dev/null
fi
if [ -x "/etc/init.d/keystone" ]   [ -e "/etc/init/keystone.conf" ]; then
invoke-rc.d keystone start   true
fi
# End automatically added section