f python?

[Xah Lee]

hi guys,

sorry am feeling a bit prolifit lately.

today's show, is: 〈Fuck Python〉
http://xahlee.org/comp/fuck_python.html

------------------------------------
**** Python
By Xah Lee, 2012-04-08

**** Python.

just fucking spend 2 hours and still going.

here's the short story.

so recently i switched to a Windows version of python. Now, Windows
version takes path using win backslash, instead of cygwin slash. This
fucking broke my find/replace scripts that takes a dir level as input.
Because i was counting slashes.

Ok no problem. My sloppiness. After all, my implementation wasn't
portable. So, let's fix it. After a while, discovered there's the
「os.sepã€. Ok, replace 「"/"〠to 「os.sepã€, done. Then, bang, all hell
went lose. Because, the backslash is used as escape in string, so any
regex that manipulate path got fucked majorly. So, now you need to
find a quoting mechanism. Then, **** python doc incomprehensible
scattered comp-sci-r-us BNF shit. Then, **** python for “os.path†and
“os†modules then string object and string functions inconsistent
ball. And **** Guido who wants to **** change python for his idiotic
OOP concept of “elegance†so that some of these are deprecated.

So after several exploration of “repr()â€, “format()â€, “‹str›.count()â€,
“os.path.normpath()â€, “re.split()â€, “len(re.search().group())†etc,
after a long time, let's use “re.escape()â€. 2 hours has passed. Also,
discovered that “os.path.walk†is now deprecated, and one is supposed
to use the sparkling “os.walkâ€. In the process of refreshing my
python, the “os.path.walk†semantics is really one fucked up ****.
Meanwhile, the “os.walk†went into incomprehensible OOP object and
iterators ****.

now, it's close to 3 hours. This fix is supposed to be done in 10 min.
I'd have done it in elisp in just 10 minutes if not for my
waywardness.

This is Before

def process_file(dummy, current_dir, file_list):
current_dir_level = len(re.split("/", current_dir)) -
len(re.split("/", input_dir))
cur_file_level = current_dir_level+1
if min_level <= cur_file_level <= max_level:
for a_file in file_list:
if re.search(r"\.html$", a_file, re.U) and
os.path.isfile(current_dir + "/" + a_file):
replace_string_in_file(current_dir + "/" + a_file)

This is After

def process_file(dummy, current_dir, file_list):
current_dir = os.path.normpath(current_dir)
cur_dir_level = re.sub( "^" + re.escape(input_dir), "",
current_dir).count( os.sep)
cur_file_level = cur_dir_level + 1
if min_level <= cur_file_level <= max_level:
for a_file in file_list:
if re.search(r"\.html$", a_file, re.U) and
os.path.isfile(current_dir + re.escape(os.sep) + a_file):
replace_string_in_file(current_dir + os.sep + a_file)
# print "%d %s" % (cur_file_level, (current_dir + os.sep +
a_file))

Complete File

# -*- coding: utf-8 -*-
# Python

# find & replace strings in a dir

import os, sys, shutil, re

# if this this is not empty, then only these files will be processed
my_files = []

input_dir = "c:/Users/h3/web/xahlee_org/lojban/hrefgram2/"
input_dir = "/cygdrive/c/Users/h3/web/zz"
input_dir = "c:/Users/h3/web/xahlee_org/"

min_level = 2; # files and dirs inside input_dir are level 1.
max_level = 2; # inclusive

print_no_change = False

find_replace_list = [

(
u"""<iframe style="width:100%;border:none" src="http://xahlee.org/
footer.html"></iframe>""",
u"""<iframe style="width:100%;border:none" src="../footer.html"></
iframe>""",
),

]

def replace_string_in_file(file_path):
"Replaces all findStr by repStr in file file_path"
temp_fname = file_path + "~lc~"
backup_fname = file_path + "~bk~"

# print "reading:", file_path
input_file = open(file_path, "rb")
file_content = unicode(input_file.read(), "utf-8")
input_file.close()

num_replaced = 0
for a_pair in find_replace_list:
num_replaced += file_content.count(a_pair[0])
output_text = file_content.replace(a_pair[0], a_pair[1])
file_content = output_text

if num_replaced > 0:
print "â—† ", num_replaced, " ", file_path.replace("\\", "/")
shutil.copy2(file_path, backup_fname)
output_file = open(file_path, "r+b")
output_file.read() # we do this way instead of “os.rename†to
preserve file creation date
output_file.seek(0)
output_file.write(output_text.encode("utf-8"))
output_file.truncate()
output_file.close()
else:
if print_no_change == True:
print "no change:", file_path

# os.remove(file_path)
# os.rename(temp_fname, file_path)

def process_file(dummy, current_dir, file_list):
current_dir = os.path.normpath(current_dir)
cur_dir_level = re.sub( "^" + re.escape(input_dir), "",
current_dir).count( os.sep)
cur_file_level = cur_dir_level + 1
if min_level <= cur_file_level <= max_level:
for a_file in file_list:
if re.search(r"\.html$", a_file, re.U) and
os.path.isfile(current_dir + re.escape(os.sep) + a_file):
replace_string_in_file(current_dir + os.sep + a_file)
# print "%d %s" % (cur_file_level, (current_dir + os.sep +
a_file))

input_dir = os.path.normpath(input_dir)

if (len(my_files) != 0):
for my_file in my_files:
replace_string_in_file(os.path.normpath(my_file) )
else:
os.path.walk(input_dir, process_file, "dummy")

print "Done."

 

[Martin P. Hellwig]

On 08/04/2012 12:11, Xah Lee wrote:
<cut all>
Hi Xah,

You clearly didn't want help on this subject, as you really now how to
do it anyway. But having read your posts over the years, I'd like to
give you an observation on your persona, free of charge!

You are actually a talented writer, some may find your occasional
profanity offensive but at least it highlights your frustration.
You are undoubtedly and proven a good mathematian and more important
than that self taught. You have a natural feel for design (otherwise you
would not clash with others view of programming).
You know a mixture of programming languages.

Whether you like it or not, you are in the perfect position to create a
new programming language and design a new programming paradigm.
Unhindered from all the legacy crap, that keep people like me behind (I
actually like BNF for example).

It is likely I am wrong, but if that is your destiny there is no point
fighting it.

Cheers and good luck,

Martin

 

[David Canzi]

hi guys,

sorry am feeling a bit prolifit lately.

today's show, is: '**** Python'
http://xahlee.org/comp/fuck_python.html

------------------------------------
**** Python
By Xah Lee, 2012-04-08

**** Python.

just fucking spend 2 hours and still going.

here's the short story.

so recently i switched to a Windows version of python. Now, Windows
version takes path using win backslash, instead of cygwin slash. This
fucking broke my find/replace scripts that takes a dir level as input.
Because i was counting slashes.

Ok no problem. My sloppiness. After all, my implementation wasn't
portable. So, let's fix it. After a while, discovered there's the
'os.sep'. Ok, replace "/" to 'os.sep', done. Then, bang, all hell
went lose. Because, the backslash is used as escape in string, so any
regex that manipulate path got fucked majorly.

When Microsoft created MS-DOS, they decided to use '\' as
the separator in file names. This was at a time when several
previously existing interactive operating systems were using
'/' as the file name separator and at least one was using '\'
as an escape character. As a result of Microsoft's decision
to use '\' as the separator, people have had to do extra work
to adapt programs written for Windows to run in non-Windows
environments, and vice versa. People have had to do extra work
to write software that is portable between these environments.
People have done extra work while creating tools to make writing
portable software easier. And people have to do extra work when
they use these tools, because using them is still harder than
writing portable code for operating systems that all used '/'
as their separator would have been.

If you added up the cost of all the extra work that people have
done as a result of Microsoft's decision to use '\' as the file
name separator, it would probably be enough money to launch the
Burj Khalifa into geosynchronous orbit.

So, when you say **** Python, are you sure you're shooting at the
right target?

 

[Kaz Kylheku]

["Followup-To:" header set to comp.lang.lisp.]

When Microsoft created MS-DOS, they decided to use '\' as
the separator in file names.

This is false. The MS-DOS (dare I say it) "kernel" accepts both forward and
backslashes as separators.

The application-level choice was once configurable through a variable
in COMMAND.COM. Then they hard-coded it to backslash.

However, Microsoft operating systems continued to (and until this day)
recognize slash as a path separator.

Only, there are broken userland programs on Windows which don't know this.

So, when you say **** Python, are you sure you're shooting at the
right target?

I would have to say, probably yes.

 

[Peter J. Holzer]

If you added up the cost of all the extra work that people have
done as a result of Microsoft's decision to use '\' as the file
name separator, it would probably be enough money to launch the
Burj Khalifa into geosynchronous orbit.

So we have another contender for the Most Expensive One-byte Mistake?

Poul-Henning Kamp nominated the C/Unix guys:

http://queue.acm.org/detail.cfm?id=2010365

hp

 

[Jürgen Exner]

Xah Lee <[email protected]> wrote:

Please check whom you are replying to.

Do not feed the trolls, please.

jue

 

[Kaz Kylheku]

So we have another contender for the Most Expensive One-byte Mistake?

The one byte mistake in DOS and Windows is recognizing two characters as path
separators. All code that correctly handles paths is complicated by having to
look for a set of characters instead of just scanning for a byte.

http://queue.acm.org/detail.cfm?id=2010365

DOS backslashes are already mentioned in that page, but alas it perpetuates the
clueless myth that DOS and windows do not recognize any other path separator.

Worse, the one byte Unix mistake being covered is, disappointingly, just a
clueless rant against null-terminated strings.

Null-terminated strings are infinitely better than the ridiculous encapsulation of length + data.

For one thing, if s is a non-empty null terminated string then, cdr(s) is also
a string representing the rest of that string without the first character,
where cdr(s) is conveniently defined as s + 1.

Not only can compilers compress storage by recognizing that string literals are
the suffixes of other string literals, but a lot of string manipulation code is
simplified, because you can treat a pointer to interior of any string as a
string.

Because they are recursively defined, you can do elegant tail recursion on null
terminated strings:

const char *rec_strchr(const char *in, int ch)
{
if (*in == 0)
return 0;
else if (*in == ch)
return in;
else
return rec_strchr(in + 1, ch);
}

length + data also raises the question: what type is the length field? One
byte? Two bytes? Four? And then you have issues of byte order. Null terminated
C strings can be written straight to a binary file or network socket and be
instantly understood on the other end.

Null terminated strings have simplified all kids of text manipulation, lexical
scanning, and data storage/communication code resulting in immeasurable
savings over the years.

 

[Nobody]

Ok no problem. My sloppiness. After all, my implementation wasn't
portable. So, let's fix it. After a while, discovered there's the
os.sep. Ok, replace "/" to os.sep, done. Then, bang, all hell
went lose. Because, the backslash is used as escape in string, so any
regex that manipulate path got fucked majorly. So, now you need to
find a quoting mechanism.

if os.altsep is not None:
sep_re = '[%s%s]' % (os.sep, os.altsep)
else:
sep_re = '[%s]' % os.sep

But really, you should be ranting about regexps rather than Python.
They're convenient if you know exactly what you want to match, but a
nuisance if you need to generate the expression based upon data which is
only available at run-time (and re.escape() only solves one very specific
problem).

 

[Xah Lee]

Xah Lee wrote:

« http://xahlee.org/comp/fuck_python.html »

David Canzi wrote

«When Microsoft created MS-DOS, they decided to use '\' as the
separator in file names.  This was at a time when several previously
existing interactive operating systems were using '/' as the file name
separator and at least one was using '\' as an escape character.  As a
result of Microsoft's decision to use '\' as the separator, people
have had to do extra work to adapt programs written for Windows to run
in non-Windows environments, and vice versa.  People have had to do
extra work to write software that is portable between these
environments. People have done extra work while creating tools to
make writing portable software easier.  And people have to do extra
work when they use these tools, because using them is still harder
than writing portable code for operating systems that all used '/' as
their separator would have been.»

yes, absolutely.  But you got 2 inaccuracies there:  1) Microsoft didn't create DOS; 2) fucking DOS was written in C, and guess what, it uses \ as escape character.  Fucking microsoft.


I agree.  **** winDOS and fucking microsoft.

No. The choice to use backslash than slash is actually a good one.

because, slash is one of the useful char, far more so than backslash.
Users should be able to use that for file names.

i don't know the detailed history of path separator, but if i were to
blame, it's **** unix. The entirety of unix, unix geek, unixers, unix
fuckheads. **** unix.

〈On Unix Filename Characters Problem〉
http://xahlee.org/UnixResource_dir/writ/unix_filename_chars.html

〈On Unix File System's Case Sensitivity〉
http://xahlee.org/UnixResource_dir/_/fileCaseSens.html

〈UNIX Tar Problem: File Length Truncation, Unicode Name Support〉
http://xahlee.org/comp/unix_tar_problem.html

〈What Characters Are Not Allowed in File Names?〉
http://xahlee.org/mswin/allowed_chars_in_file_names.html

〈Unicode Support in File Names: Windows, Mac, Emacs, Unison, Rsync,
USB, Zip〉
http://xahlee.org/mswin/unicode_support_file_names.html

〈The Nature of the Unix Philosophy〉
http://xahlee.org/UnixResource_dir/writ/unix_phil.html

Xah

 

[Roy Smith]

Null terminated strings have simplified all kids of text
manipulation, lexical scanning, and data storage/communication
code resulting in immeasurable savings over the years.

Yeah, especially code that needs to deal with lengths and nulls. It's
great for buffer overruns too.[/QUOTE]

I once worked on a C++ project that used a string class which kept a
length count, but also allocated one extra byte and stuck a null at the
end of every string.

 

[Kaz Kylheku]

Are you really too clueless to differentiate between C and LISP?

In Lisp we can burn a list literal like '(a b c) into ROM, and compute (b c)
without allocating any memory.

Null-terminated C strings do the same thing.

In some Lisp systems, in fact, "CDR coding" was used to save space when
allocating a list all at once. This created something very similar to
a C string: a vector-like object of all the CARs, with a terminating
convention marking the end.

It's logically very similar.

I need not repeat the elegant recursion example for walking a C string.

That example is not possible with the length + data representation.
(Not without breaking the encapsulation and passing the length as a separate
recursion parameter to a recursive routine that works with the raw data part of
the string.)

Yeah, especially code that needs to deal with lengths and nulls.

To get the length of a string, you call a function, in either representation,
so it is not any more complicated from a coding point of view. The function is,
of course, more expensive if the string is null terminated, but you can code
with awareness of this and not call length wastefully.

If all else was equal (so that the expense of the length operation were
the /only/ issue) then of course the length + data would be better.

However, all else is not equal.

One thing that is darn useful, for instance, is that
p + strlen(p) still points to a string which is length zero, and this
sort of thing is widely exploited in text processing code. e.g.

size_t digit_prefix_len = strspn(input_string, "0123456789");
const char *after_digits = input-string + digit_prefix_len;

if (*after_digits == 0) {
/* string consists only of digits: nothing after digits */
} else {
/* process part after digits */
}

It's nice that after_digits is a bona-fide string just like input_string,
without any memory allocation being required.

We can lexically analyze a string without ever asking it what its length is,
and as we march down the string, the remaining suffix of that string is always
a string so we can treat it as one, recurse on it, whatever.

Code that needs to deal with null "characters" is manipulating binary data, not
text, and should use a suitable data structure for that.

It's great for buffer overruns too.

If we scan for a null terminator which is not there, we have a buffer overrun.

If a length field in front of string data is incorrect, we also have a buffer
overrrun.

A pattern quickly emerges here: invalid, corrupt data produced by buggy code
leads to incorrect results, and behavior that is not well-defined!

 

[Kaz Kylheku]

Yeah, especially code that needs to deal with lengths and nulls. It's
great for buffer overruns too.

I once worked on a C++ project that used a string class which kept a
length count, but also allocated one extra byte and stuck a null at the
end of every string.[/QUOTE]

Me too! I worked on numerous C++ projects with such a string template
class.

It was usually called

std::basic_string

and came from this header called:

#include <string>

which also instantiated it into two flavors under two nicknames:
std::basic_string<char> being introduced as std::string, and
std::basic_string<wchar_t> as std::wstring.

This class had a c_str() function which retrieved a null-terminated
string and so most implementations just stored the data that way, but
some of the versions of that class cached the length of the string
to avoid doing a strlen or wcslen operation on the data.

 

[Rainer Weikusat]

[...]

Are you really too clueless to differentiate between C and LISP?

In LISP, a list is a set of conses (pairs) whose car (first element of
the pair) contains a value and whose cdr (second element of the pair)
links to the next cons that's part of the list. The end of a list is
marked by a cdr whose value is nil. A so-called 'C string' is a
sequentially allocated sequence of memory locations which contain the
characters making up the string and the end of it is marked by a
memory location holding the value 0. This is logically very similar
to the LISP list and it shouldn't be to difficult to understand that
'cdr(s) is also a string representing the rest of the string' means
'given that s points to a non-empty C string, s + 1 points to a
possibly empty C string which is identical with s with the first
character removed'.

Yeah, especially code that needs to deal with lengths and nulls. It's
great for buffer overruns too.

This is, I think, a case where the opinions of people who have used C
strings and the opinions of people who haven't differ greatly. A nice
German proverb applicable to situations like that would be 'Was der
Bauer nicht kennt das frisst er nicht' ...

 

[Rainer Weikusat]

[...]

Are you really too clueless to differentiate between C and LISP?

In LISP, a list is a set of conses (pairs) whose car (first element of
the pair) contains a value and whose cdr (second element of the pair)
links to the next cons that's part of the list. The end of a list is
marked by a cdr whose value is nil.

Addition: This can also be implemented very neatly in Perl by using
two element array references as 'cons cells', toy example

-----------
sub car
{
return $_[0][0];
}

sub cdr
{
return $_[0][1];
}

sub list
{
@_ && [shift, &list];
}

$l = list(0 .. 100);
while ($l) {
print(car($l), ' ');
$l = cdr($l);
}
print("\n");

 

[BartC]

In <[email protected]>, on 04/09/2012
at 06:55 PM, Kaz Kylheku <[email protected]> said:

You're only thinking of scanning an existing string; think of
constructing a string. The null only indicates the current length, not
the amount allocated.


The languages that I'm aware of that use a string length field also
use a length field for the allocated storage. More precisely, they
require that attempts to store beyond the allocated length be
detected.

I would have thought trying to *read* beyond the current length would be an
error.

Writing beyond the current length, and perhaps beyond the current allocation
might be OK if the string is allowed grow, otherwise that's also an error.

In any case, there is no real need for an allocated length to be passed
around with the string, if you are only going to be reading it, or only
modifying the existing characters. And depending on the memory management
arrangements, such a length need not be stored at all.

 

[Rainer Weikusat]

C arrays are not LISP strings; there is no C analog to car and cdr.

'car' and 'cdr' refer to cons cells in Lisp, not to strings. How the
first/rest terminology can be sensibly applied to 'C strings' (which
are similar to linked-lists in the sense that there's a 'special
termination value' instead of an explicit length) was already
explained elsewhere.

 

[WJ]

so recently i switched to a Windows version of python. Now, Windows
version takes path using win backslash, instead of cygwin slash. This
fucking broke my find/replace scripts that takes a dir level as input.
Because i was counting slashes.

Slashes can work under windows, up to a point:

C:\>cd info/source

C:\info\source>


Also, most languages I use under windows allow you to use
slashes in paths:

C:\>ruby -e "puts IO.read( 'c:/info/frag' )"
275439
109999
102972
109999
102972
110000
102972
109999

101085
108111

 

[Kaz Kylheku]

["Followup-To:" header set to comp.lang.lisp.]

A syringe is similar to a sturgeon in the sense that they both start
with S. LISP doesn't have arrays, and C doesn't allow you to insert
into the middle of an array.

Lisp, however, has arrays. (Not to mention hash tables, structures, and
classes). Where have you been since 1960-something?

(let ((array #(1 2 3 4)))
(aref array 3)) ;; -> 4, O(1) access

 

[Rainer Weikusat]

A syringe is similar to a sturgeon in the sense that they both start
with S.

And the original definition of 'idiot' is 'a guy who cannot learn
because he is too cocksure to already know everything'. Not that this
would matter in the given context ...

LISP doesn't have arrays,

Lisp has arrays.

and C doesn't allow you to insert
into the middle of an array.

Well, of course it does: You just have to move the content of all
memory cells 'after' the new insert 'one up'. But unless I'm very much
mistaken, the topic was "first and rest" (car and cdr), as the terms
could be used with a C string and not "whatever Shmuel happens to
believe to know" ...

 

[Pascal J. Bourguignon]

A syringe is similar to a sturgeon in the sense that they both start
with S. LISP doesn't have arrays, and C doesn't allow you to insert
into the middle of an array.

You're confused. C doesn't have arrays. Lisp has arrays.
C only has vectors (Lisp has vectors too).

That C calls its vectors "array", or its bytes "char" doesn't change the
fact that C has no array and no character.


cl-user> (make-array '(3 4 5) :initial-element 42)
#3A(((42 42 42 42 42) (42 42 42 42 42) (42 42 42 42 42) (42 42 42 42 42))
((42 42 42 42 42) (42 42 42 42 42) (42 42 42 42 42) (42 42 42 42 42))
((42 42 42 42 42) (42 42 42 42 42) (42 42 42 42 42) (42 42 42 42 42)))

cl-user> (make-array 10 :initial-element 42)
#(42 42 42 42 42 42 42 42 42 42)