比較perl+python

 

http://hyperpolyglot.org/scripting 

 

 

比較perl+python  

 

	perl (1987)	python (1991)
基礎
模塊導入	use strict;	import os, re, sys
版本查看	$ perl -v	$ python -V
執行腳本	$ perl foo.pl	$ python foo.py
交互模式	$ perl -de 0	$ python
執行語句	$ perl -e 'print("hi\n")'	$ python -c "print('hi')"
語句分隔	;	\n (newline) or ;
語句塊	{}	Indent
注釋	# comment	# comment
多行注釋	=for comment line another line =cut	use triple quote string literal: '''comment line another line'''
變量和操作符
賦值	$v = 1;	v = 1
賦值	($x, $y, $z) = (1, 2, 3); # 3 is discarded: ($x, $y) = (1, 2, 3); # $z set to undef: ($x, $y, $z) = (1, 2);	x, y, z = 1, 2, 3 # raises ValueError: x, y = 1, 2, 3 # raises ValueError: x, y, z = 1, 2
交換	($x, $y) = ($y, $x);	x, y = y, x
操作符	+= -= *= none /= %= **= .= x= &&= ||= ^= <<= >>= &= |= ^=	# do not return values: += -= *= /= //= %= **= += *= &= |= ^= <<= >>= &= |= ^=
自增	my $x = 1; my $y = ++$x; my $z = --$y;	none
局部變量	my $v; my (@a, %d); my $x = 1; my ($y, $z) = (2, 3);	# in function body: v = None a, d = [], {} x = 1 y, z = 2, 3
全局變量	our ($g1, $g2) = (7, 8); sub swap_globals {   ($g1, $g2) = ($g2, $g1); }	g1, g2 = 7, 8 def swap_globals():   global g1, g2   g1, g2 = g2, g1
常量	use constant PI => 3.14;	# uppercase identifiers # constant by convention PI = 3.14
空	undef	None
空測試	! defined $v	v == None v is None
訪問未定義變量	error under use strict; otherwise undef	raises NameError
真假	1 ""	True False
假	undef 0 0.0 "" "0" ()	False None 0 0.0 '' [] {}
邏輯運算	&& || ! lower precedence: and or xor not	and or not
條件	$x > 0 ? $x : -$x	x if x > 0 else -x
比較	numbers only: == != > < >= <= strings: eq ne gt lt ge le	comparison operators are chainable: == != > < >= <=
數學運算
類型轉化	7 + "12" 73.9 + ".037" "value: " . 8	7 + int('12') 73.9 + float('.037') 'value: ' + str(8)
算術運算	+ - * / none % **	+ - * / // % **
取余	int ( 13 / 5 ) none	13 // 5 q, r = divmod(13, 5)
浮點除法	13 / 5	float(13) / 5 # Python 3: 13 / 5
數學函數	use Math::Trig qw(   tan asin acos atan); sqrt exp log sin cos tan asin acos atan atan2	from math import sqrt, exp, log, \ sin, cos, tan, asin, acos, atan, atan2
四舍五入	# cpan -i Number::Format use Number::Format 'round'; use POSIX qw(ceil floor); int($x) round($x, 0) ceil($x) floor($x) abs($x)	import math int(x) int(round(x)) math.ceil(x) math.floor(x) abs(x)
最大最小	use List::Util qw(min max); min(1,2,3); max(1,2,3); @a = (1,2,3); min(@a); max(@a);	min(1,2,3) max(1,2,3) min([1,2,3]) max([1,2,3])
除0	error	raises ZeroDivisionError
大整數	converted to float; use Math::BigInt to create arbitrary length integers	becomes arbitrary length integer of type long
大浮點數	inf	raises OverflowError
隨機數	int(rand() * 100) rand() none	import random random.randint(0,99) random.random() random.gauss(0,1)
隨機數	srand 17; my $sd = srand; srand($sd);	import random random.seed(17) sd = random.getstate() random.setstate(sd)
位操作	<< >> & | ^ ~	<< >> & | ^ ~
其他進制	0b101010 052 0x2a	0b101010 052 0x2a
字符串操作
字符串	"don't say \"no\"" 'don\'t say "no"'	'don\'t say "no"' "don't say \"no\"" "don't " 'say "no"' '''don't say "no"''' """don't say "no\""""
多行字符串	yes	triple quote literals only
轉義	double quoted: \a \b \cx \e \f \n \r \t \xhh \x{hhhh} \ooo   Perl 5.14: \o{ooo} single quoted: \' \\	single and double quoted: \newline \\ \' \" \a \b \f \n \r \t \v \ooo \xhh Python 3: \uhhhh \Uhhhhhhhh
變量替換	my $count = 3; my $item = "ball"; print "$count ${item}s\n";	count = 3 item = 'ball' print(‘%s %s’ % (count, item))
sprintf	my $fmt = "lorem %s %d %f"; sprintf($fmt, "ipsum", 13, 3.7)	'lorem %s %d %f' % ('ipsum', 13, 3.7) fmt = 'lorem {0} {1} {2}' fmt.format('ipsum', 13, 3.7)
here document	$word = "amet"; $s = <<EOF; lorem ipsum dolor sit $word EOF	‘’’ ‘’’
字符串連接	my $s = "Hello, "; my $s2 = $s . "World!";	s = 'Hello, ' s2 = s + 'World!' juxtaposition can be used to concatenate literals: s2 = 'Hello, ' "World!"
字符串復制	my $hbar = "-" x 80;	hbar = '-' * 80
字符串分隔	split(/\s+/, "do re mi fa") split(/\s+/, "do re mi fa", 2) split(/(\s+)/, "do re mi fa"); split(//, "abcd")	'do re mi fa'.split() 'do re mi fa'.split(None, 1) re.split('(\s+)', 'do re mi fa') list('abcd')
字符串連接	join(" ", qw(do re mi fa))	' '.join(['do', 're', 'mi', 'fa'])
字符串大小寫	uc("lorem") lc("LOREM") ucfirst("lorem")	'lorem'.upper() 'LOREM'.lower() 'lorem'.capitalize()
字符串strip	# cpan -i Text::Trim use Text::Trim; trim " lorem " ltrim " lorem" rtrim "lorem "	' lorem '.strip() ' lorem'.lstrip() 'lorem '.rstrip()
字符串格式化	sprintf("%-10s", "lorem") sprintf("%10s", "lorem")	'lorem'.ljust(10) 'lorem'.rjust(10)
字符串長度	length("lorem")	len('lorem')
字符串index	index("lorem ipsum", "ipsum") rindex("do re re", "re") return -1 if not found	'do re re'.index('re') 'do re re'.rindex('re') raise ValueError if not found
子字符串	substr("lorem ipsum", 6, 5)	'lorem ipsum'[6:11]
訪問字符串中字母	can't use index notation with strings: substr("lorem ipsum", 6, 1)	'lorem ipsum'[6]
字母數字轉化	chr(65) ord("A")	chr(65) ord('A')
正則表達式
字符串或	/lorem|ipsum/ qr(/etc/hosts)	re.compile('lorem|ipsum') none
特殊字符	char class abbrevs: . \d \D \h \H \s \S \v \V \w \W anchors: ^ $ \A \b \B \z \Z	char class abbrevs: . \d \D \s \S \w \W anchors: ^ $ \A \b \B \Z
正則表達式匹配	if ($s =~ /1999/) {   print "party!\n"; }	if re.search('1999', s):   print('party!')
忽略大小寫	"Lorem" =~ /lorem/i	re.search('lorem', 'Lorem', re.I)
選項	i m s p x	re.I re.M re.S re.X
替換	my $s = "do re mi mi mi"; $s =~ s/mi/ma/g;	s = 'do re mi mi mi' s = re.compile('mi').sub('ma', s)
group	$rx = qr/(\d{4})-(\d{2})-(\d{2})/; "2010-06-03" =~ $rx; ($yr, $mo, $dy) = ($1, $2, $3);	rx = '(\d{4})-(\d{2})-(\d{2})' m = re.search(rx, '2010-06-03') yr, mo, dy = m.groups()
findall	my $s = "dolor sit amet"; @a = $s =~ m/\w+/g;	s = 'dolor sit amet' a = re.findall('\w+', s)
匹配引用	"do do" =~ /(\w+) \1/ my $s = "do re"; $s =~ s/(\w+) (\w+)/$2 $1/;	none rx = re.compile('(\w+) (\w+)') rx.sub(r'\2 \1', 'do re')
日期時間
日期時間類型	Time::Piece if use Time::Piece in effect, otherwise tm array	datetime.datetime
當前日期時間	use Time::Piece; my $t = localtime(time); my $utc = gmtime(time);	import datetime t = datetime.datetime.now() utc = datetime.datetime.utcnow()
與epoch轉化	use Time::Local; use Time::Piece; my $epoch = timelocal($t); my $t2 = localtime(1304442000);	from datetime import datetime as dt epoch = int(t.strftime("%s")) t2 = dt.fromtimestamp(1304442000)
當前epoch	$epoch = time;	import datetime t = datetime.datetime.now() epoch = int(t.strftime("%s"))
strftime	use Time::Piece; $t = localtime(time); $fmt = "%Y-%m-%d %H:%M:%S"; print $t->strftime($fmt);	t.strftime('%Y-%m-%d %H:%M:%S')
默認格式	Tue Aug 23 19:35:19 2011	2011-08-23 19:35:59.411135
字符串轉為時間strptime	use Time::Local; use Time::Piece; $s = "2011-05-03 10:00:00"; $fmt = "%Y-%m-%d %H:%M:%S"; $t = Time::Piece->strptime($s,$fmt);	from datetime import datetime s = '2011-05-03 10:00:00' fmt = '%Y-%m-%d %H:%M:%S' t = datetime.strptime(s, fmt)
解析日期	# cpan -i Date::Parse use Date::Parse; $epoch = str2time("July 7, 1999");	# pip install python-dateutil import dateutil.parser s = 'July 7, 1999' t = dateutil.parser.parse(s)
時間差	Time::Seconds object if use Time::Piece in effect; not meaningful to subtract tm arrays	datetime.timedelta object
時間運算	use Time::Seconds; $now = localtime(time); $now += 10 * ONE_MINUTE() + 3;	import datetime delta = datetime.timedelta(   minutes=10,   seconds=3) t = datetime.datetime.now() + delta
時區	Time::Piece has local timezone if created withlocaltime and UTC timezone if created with gmtime; tm arrays have no timezone or offset info	a datetime object has no timezone information unless a tzinfo object is provided when it is created
timezone name; offset from UTC; 是否夏令時	# cpan -i DateTime use DateTime; use DateTime::TimeZone; $dt = DateTime->now(); $tz = DateTime::TimeZone->new(   name=>"local"); $tz->name; $tz->offset_for_datetime($dt) /   3600; $tz->is_dst_for_datetime($dt);	import time tm = time.localtime()    time.tzname[tm.tm_isdst] (time.timezone / -3600) + tm.tm_isdst tm.tm_isdst
microseconds	use Time::HiRes qw(gettimeofday); ($sec, $usec) = gettimeofday;	t.microsecond
sleep	a float argument will be truncated to an integer: sleep 1;	import time time.sleep(0.5)
timeout	eval {   $SIG{ALRM}= sub {die "timeout!";};   alarm 5;   sleep 10; }; alarm 0;	import signal, time class Timeout(Exception): pass def timeout_handler(signo, fm):   raise Timeout() signal.signal(signal.SIGALRM,   timeout_handler) try:   signal.alarm(5)   time.sleep(10) except Timeout:   pass signal.alarm(0)
數組
定義	@a = (1, 2, 3, 4);	a = [1, 2, 3, 4]
quote words	@a = qw(do re mi);	none
長度	$#a + 1 or scalar(@a)	len(a)
空測試	!@a	not a
使用	$a[0]	a[0]
更新	$a[0] = "lorem";	a[0] = 'lorem'
越界訪問	@a = (); evaluates as undef: $a[10]; increases array size to 11: $a[10] = "lorem";	a = [] raises IndexError: a[10] raises IndexError: a[10] = 'lorem'
index	use List::Util 'first'; @a = qw(x y z w); $i = first {$a[$_] eq "y"} (0..$#a);	a = ['x', 'y', 'z', 'w'] i = a.index('y')
子數組	select 3rd and 4th elements: @a[2..3] splice(@a, 2, 2)	select 3rd and 4th elements: a[2:4] none
子數組	@a[1..$#a]	a[1:]
添加刪除	@a = (6,7,8); push @a, 9; pop @a;	a = [6,7,8] a.append(9) a.pop()
插入刪除	@a = (6,7,8); unshift @a, 5; shift @a;	a = [6,7,8] a.insert(0,5) a.pop(0)
數組連接	@a = (1,2,3); @a2 = (@a,(4,5,6)); push @a, (4,5,6);	a = [1,2,3] a2 = a + [4,5,6] a.extend([4,5,6])
初始化	@a = (undef) x 10;	a = [None] * 10 a = [None for i in range(0, 10)]
淺拷貝深拷貝	use Storable 'dclone' my @a = (1,2,[3,4]); my $a2 = \@a; my @a3 = @a; my @a4 = @{dclone(\@a)};	import copy a = [1,2,[3,4]] a2 = a a3 = list(a) a4 = copy.deepcopy(a)
數組作為函數參數	each element passed as separate argument; use reference to pass array as single argument	parameter contains address copy
遍歷	for $i (1, 2, 3) { print "$i\n" }	for i in [1,2,3]:   print(i)
遍歷	none; use range iteration from 0 to $#a and use index to look up value in the loop body	a = ['do', 're', 'mi', 'fa'] for i, s in enumerate(a):   print('%s at index %d' % (s, i))
range	for $i (1..1_000_000) {   code }	range replaces xrange in Python 3: for i in xrange(1, 1000001):   code
range數組	@a = 1..10;	a = range(1, 11) Python 3: a = list(range(1, 11))
翻轉	@a = (1,2,3); reverse @a; @a = reverse @a;	a = [1,2,3] a[::-1] a.reverse()
排序	@a = qw(b A a B); sort @a; @a = sort @a; sort { lc($a) cmp lc($b) } @a;	a = ['b', 'A', 'a', 'B'] sorted(a) a.sort() a.sort(key=str.lower)
去重復	use List::MoreUtils 'uniq'; my @a = (1,2,2,3); my @a2 = uniq @a; @a = uniq @a;	a = [1,2,2,3] a2 = list(set(a)) a = list(set(a))
是否存在於數組	7 ~~ @a	7 in a
集合交集		{1,2} & {2,3,4}
集合或		{1,2} | {2,3,4}
集合運算		{1,2,3} - {2} {1,2} ^ {2,3,4}
map	map { $_ * $_ } (1,2,3)	map(lambda x: x * x, [1,2,3]) # or use list comprehension: [x*x for x in [1,2,3]]
filter	grep { $_ > 1 } (1,2,3)	filter(lambda x: x > 1, [1,2,3]) # or use list comprehension: [x for x in [1,2,3] if x > 1]
reduce	use List::Util 'reduce'; reduce { $x + $y } 0, (1,2,3)	# import needed in Python 3 only from functools import reduce reduce(lambda x, y: x+y, [1,2,3], 0)
All/any	# cpan -i List::MoreUtils use List::MoreUtils qw(all any); all { $_ % 2 == 0 } (1,2,3,4) any { $_ % 2 == 0 } (1,2,3,4)	all(i%2 == 0 for i in [1,2,3,4]) any(i%2 == 0 for i in [1,2,3,4])
shuffle and sample	use List::Util 'shuffle'; @a = (1, 2, 3, 4); shuffle(@a); none	from random import shuffle, sample a = [1, 2, 3, 4] shuffle(a) sample(a, 2)
zip	# cpan -i List::MoreUtils use List::MoreUtils 'zip'; @nums = (1, 2, 3); @lets = qw(a b c); # flat array of 6 elements: @a = zip @nums, @lets;	# array of 3 pairs: a = zip([1,2,3], ['a', 'b', 'c'])
字典對象
定義	%d = ( t => 1, f => 0 );	d = { 't':1, 'f':0 }
size	scalar(keys %d)	len(d)
lookup	$d{"t"}	d['t']
out-of-bounds behavior	%d = (); evaluates as undef: $d{"lorem"}; adds key/value pair: $d{"lorem"} = "ipsum";	d = {} raises KeyError: d['lorem'] adds key/value pair: d['lorem'] = 'ipsum'
is key present	exists $d{"y"}	'y' in d
delete entry	%d = ( 1 => "t", 0 => "f" ); delete $d{1};	d = {1: True, 0: False} del d[1]
from array of pairs, from even length array	@a = (1,"a",2,"b",3,"c"); %d = @a;	a = [[1,'a'], [2,'b'], [3,'c']] d = dict(a) a = [1,'a',2,'b',3,'c'] d = dict(zip(a[::2], a[1::2]))
merge	%d1 = (a=>1, b=>2); %d2 = (b=>3, c=>4); %d1 = (%d1, %d2);	d1 = {'a':1, 'b':2} d2 = {'b':3, 'c':4} d1.update(d2) # {'a': 1, 'c': 4, 'b': 3}
invert	%to_num = (t=>1, f=>0); %to_let = reverse %to_num;	to_num = {'t':1, 'f':0} # dict comprehensions added in 2.7: to_let = {v:k for k, v   in to_num.items()}
iteration	while ( ($k, $v) = each %d ) {   code }	for k, v in d.iteritems():   code Python 3: for k, v in d.items():   code
keys and values as arrays	keys %d values %d	d.keys() d.values() Python 3: list(d.keys()) list(d.values())
default value, computed value	my %counts; $counts{'foo'} += 1 define a tied hash for computed values and defaults other than zero or empty string	from collections import defaultdict counts = defaultdict(lambda: 0) counts['foo'] += 1 class Factorial(dict):   def __missing__(self, k):     if k > 1:       return k * self[k-1]     else:       return 1 factorial = Factorial()
函數
函數申明	sub add { $_[0] + $_[1] } sub add {   my ($a, $b) = @_;   $a + $b; }	def add(a, b):   return a+b
函數調用	add(1, 2); parens are optional: add 1, 2;	add(1, 2)
參數丟失	set to undef	raises TypeError
參數默認值	sub my_log {   my $x = shift;   my $base = shift // 10;   log($x)/log($base); } my_log(42); my_log(42, exp(1));	import math def my_log(x, base=10):   return math.log(x)/math.log(base) my_log(42) my_log(42, math.e)
變長參數	sub foo {   if ( @_ >= 1 ) {     print "first: $_[0]\n";   }   if ( @_ >= 2 ) {     print "last: $_[-1]\n";   } }	def foo(*a):   if len(a) >= 1:     print('first: ' + str(a[0]))   if len(a) >= 2:     print('last: ' + str(a[-1]))
命名參數	none	def fequal(x, y, **opts):   eps = opts.get('eps') or 0.01   return abs(x - y) < eps fequal(1.0, 1.001) fequal(1.0, 1.001, eps=0.1**10)
pass number or string by reference	sub foo {   $_[0] += 1;   $_[1] .= "ly"; } my $n = 7; my $s = "hard"; foo($n, $s);	not possible
pass array or dictionary by reference	sub foo {   $_[0][2] = 5;   $_[1]{"f"} = -1; } my @a = (1,2,3); my %d = ("t"=> 1, "f" => 0); foo(\@a, \%d);	def foo(x, y):   x[2] = 5   y['f'] = -1 a = [1,2,3] d = {'t':1, 'f':0} foo(a, d)
return value	return arg or last expression evaluated	return arg or None
multiple return values	sub first_and_second {   return ($_[0], $_[1]); } @a = (1,2,3); ($x, $y) = first_and_second(@a);	def first_and_second(a):   return a[0], a[1] x, y = first_and_second([1,2,3])
lambda declaration	$sqr = sub { $_[0] * $_[0] }	body must be an expression: sqr = lambda x: x * x
lambda invocation	$sqr->(2)	sqr(2)
function reference	my $func = \&add;	func = add
function with private state	use feature state; sub counter {   state $i = 0;   ++$i; } print counter() . "\n";	# state not private: def counter():   counter.i += 1   return counter.i counter.i = 0 print(counter())
closure	sub make_counter {   my $i = 0;   return sub { ++$i }; } my $nays = make_counter; print $nays->() . "\n";	# Python 3: def make_counter():   i = 0   def counter():     nonlocal i     i += 1     return i   return counter nays = make_counter()
generator	none	def make_counter():   i = 0   while True:     i += 1     yield i nays = make_counter() print(nays.next())
decorator		def logcall(f):   def wrapper(*a, **opts):     print('calling ' + f.__name__)     f(*a, **opts)     print('called ' + f.__name__)   return wrapper @logcall def square(x):   return x * x square(5)
流程控制
if	if ( 0 == $n ) {   print "no hits\n" } elsif ( 1 == $n ) {   print "one hit\n" } else {   print "$n hits\n" }	if 0 == n:   print('no hits') elif 1 == n:   print('one hit') else:   print(str(n) + ' hits')
switch	use feature 'switch'; given ($n) {   when (0) { print "no hits\n"; }   when (1) { print "one hit\n"; }   default { print "$n hits\n"; } }	none
while	while ( $i < 100 ) { $i++ }	while i < 100:   i += 1
c-style for	for ( $i=0; $i <= 10; $i++ ) {   print "$i\n"; }	none
Foreach	@a = (1..5); foreach  (@a) {    print "$_\n"; }   @a = (1..5); for (@a) {    print "$_\n" }	a = ['do', 're', 'mi', 'fa'] for i, s in enumerate(a):   print('%s at index %d' % (s, i))   for i in [1,2,3]:   print(i)
break, continue, redo	last next redo	break continue none
control structure keywords	do else elsif for foreach goto if unless until while	elif else for if while
what do does	executes following block and returns value of last statement executed	raises NameError unless a value was assigned to it
statement modifiers	print "positive\n" if $i > 0; print "nonzero\n" unless $i == 0;	none
raise exception	die "bad arg";	raise Exception('bad arg')
catch exception	eval { risky }; if ($@) {   print "risky failed: $@\n"; }	try:   risky() except:   print('risky failed')
global variable for last exception	$EVAL_ERROR: $@ $OS_ERROR: $! $CHILD_ERROR: $?	last exception: sys.exc_info()[1]
define exception	none	class Bam(Exception):   def __init__(self):     super(Bam, self).__init__('bam!')
catch exception by type	none	try:   raise Bam() except Bam as e:   print(e)
finally/ensure	none	acquire_resource() try:   risky() finally:   release_resource()
start thread	use threads; $func = sub { sleep 10 }; $thr = threads->new($func);	class sleep10(threading.Thread):   def run(self):     time.sleep(10) thr = sleep10() thr.start()
wait on thread	$thr->join;	thr.join()
文件和輸出
print to standard output	print "Hello, World!\n";	print('Hello, World!')
read from standard input	$line = <STDIN>;	line = sys.stdin.readline()
standard file handles	STDIN STDOUT STDERR	sys.stdin sys.stdout sys.stderr
open file	open my $f, "/etc/hosts"; or open FILE, "/etc/hosts";	f = open('/etc/hosts')
open file for writing	open my $f, ">/tmp/perl_test"; or open FILE, ">/tmp/perl_test";	f = open('/tmp/test', 'w')
open file for append		with open('/tmp/test') as f:   f.write('lorem ipsum\n')
close file	close $f; or close FILE;	f.close()
read line	$line = <$f>; or $line = <FILE>;	f.readline()
iterate over file by line	while ($line = <$f>) {	for line in f:
chomp	chomp $line;	line = line.rstrip('\r\n')
read entire file into array or string	@a = <$f>; $s = do { local $/; <$f> };	a = f.readlines() s = f.read()
write to file	print $f "lorem ipsum";	f.write('lorem ipsum')
flush file handle	use IO::Handle; $f->flush();	f.flush()
file test, regular file test	If (-e "/etc/hosts") {print exist;} -f "/etc/hosts"	os.path.exists('/etc/hosts') os.path.isfile('/etc/hosts')
copy file, remove file, rename file	use File::Copy; copy("/tmp/foo", "/tmp/bar"); unlink "/tmp/foo"; move("/tmp/bar", "/tmp/foo"); unlink();	import shutil shutil.copy('/tmp/foo', '/tmp/bar') os.remove('/tmp/foo') shutil.move('/tmp/bar', '/tmp/foo') os.remove()
set file permissions	chmod 0755, "/tmp/foo";	os.chmod('/tmp/foo', 0755)
temporary file	use File::Temp; $f = File::Temp->new(); print $f "lorem ipsum\n"; close $f; print "tmp file: "; print $f->filename . "\n";	import tempfile f = tempfile.NamedTemporaryFile(   prefix='foo') f.write('lorem ipsum\n') f.close() print("tmp file: %s" % f.name)
in memory file	my ($f, $s); open($f, ">", \$s); print $f "lorem ipsum\n"; $s;	from StringIO import StringIO f = StringIO() f.write('lorem ipsum\n') s = f.getvalue() Python 3 moved StringIO to the io module
目錄操作
build pathname	use File::Spec; File::Spec->catfile("/etc", "hosts")	os.path.join('/etc', 'hosts')
dirname and basename	use File::Basename; print dirname("/etc/hosts"); print basename("/etc/hosts");	os.path.dirname('/etc/hosts') os.path.basename('/etc/hosts')
absolute pathname	use Cwd; Cwd::abs_path("..")	os.path.abspath('..')
iterate over directory by file	use File::Basename; while ( </etc/*> ) {    print basename($_) . "\n"; }	for filename in os.listdir('/etc'):   print(filename)
make directory	use File::Path 'make_path'; make_path "/tmp/foo/bar";	dirname = '/tmp/foo/bar' if not os.path.isdir(dirname):   os.makedirs(dirname)
recursive copy	# cpan -i File::Copy::Recursive use File::Copy::Recursive 'dircopy'; dircopy "/tmp/foodir",   "/tmp/bardir";	import shutil shutil.copytree('/tmp/foodir',   '/tmp/bardir')
remove empty directory	rmdir "/tmp/foodir";	os.rmdir('/tmp/foodir')
remove directory and contents	use File::Path 'remove_tree'; remove_tree "/tmp/foodir";	import shutil shutil.rmtree('/tmp/foodir')
directory test	-d "/tmp"	os.path.isdir('/tmp')
命令行操作
command line args, script name	scalar(@ARGV) $ARGV[0] $ARGV[1] etc $0	len(sys.argv)-1 sys.argv[1] sys.argv[2] etc sys.argv[0]
getopt	use Getopt::Long; my ($src, $help); sub usage {   print "usage: $0 --f SRC\n";   exit -1; } GetOptions("file=s" => \$src,   "help" => \$help); usage if $help;	import argparse parser = argparse.ArgumentParser() parser.add_argument('--file', '-f',   dest='file') args = parser.parse_args() src = args.file
get and set environment variable	$ENV{"HOME"} $ENV{"PATH") = "/bin";	os.getenv('HOME') os.environ['PATH'] = '/bin'
exit	exit 0;	sys.exit(0)
set signal handller	$SIG{INT} = sub {   die "exiting…\n"; };	import signal def handler(signo, frame):   print('exiting…')   exit -1 signal.signal(signal.SIGINT, handler)
executable test	-x "/bin/ls"	os.access('/bin/ls', os.X_OK)
external command	system("ls -l /tmp") == 0 or   die "ls failed";	if os.system('ls -l /tmp'):   raise Exception('ls failed')
escaped external command	$path = <>; chomp($path); system("ls", "-l", $path) == 0 or   die "ls failed";	import subprocess cmd = ['ls', '-l', '/tmp'] if subprocess.call(cmd):   raise Exception('ls failed')
backticks	my $files = `ls -l /tmp`; or my $files = qx(ls);	import subprocess cmd = ['ls', '-l', '/tmp'] files = subprocess.check_output(cmd)
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完！