比较perl+python的优点和缺点

	perl (1987)	python (1991)
基础
模块导入	use strict;	import os, re, sys
版本查看	$ perl -v	$ python -V
执行脚本	$ perl foo.pl	$ python foo.py
交互模式	$ perl -de 0	$ python
执行语句	$ perl -e 'print("hi\n")'	$ python -c "print('hi')"
语句分隔	;	\n (newline) or ;
语句块	{}	Indent
注释	# comment	# comment
多行注释	=for comment line another line =cut	use triple quote string literal: '''comment line another line'''
变量和操作符
赋值	$v = 1;	v = 1
赋值	($x, $y, $z) = (1, 2, 3); # 3 is discarded: ($x, $y) = (1, 2, 3); # $z set to undef: ($x, $y, $z) = (1, 2);	x, y, z = 1, 2, 3 # raises ValueError: x, y = 1, 2, 3 # raises ValueError: x, y, z = 1, 2
交换	($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
局部变量	my $v; my (@a, %d); my $x = 1; my ($y, $z) = (2, 3);	# in function body: v = None a, d = [], {} x = 1 y, z = 2, 3
全局变量	our ($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
空测试	! defined $v	v == None v is None
访问未定义变量	error under use strict; otherwise undef	raises NameError
真假	1 ""	True False
假	undef 0 0.0 "" "0" ()	False None 0 0.0 '' [] {}
逻辑运算	&& || ! lower precedence: and or xor not	and or not
条件	$x > 0 ? $x : -$x	x if x > 0 else -x
比较	numbers only: == != > < >= <= strings: eq ne gt lt ge le	comparison operators are chainable: == != > < >= <=
数学运算
类型转化	7 + "12" 73.9 + ".037" "value: " . 8	7 + int('12') 73.9 + float('.037') 'value: ' + str(8)
算术运算	+ - * / none % **	+ - * / // % **
取余	int ( 13 / 5 ) none	13 // 5 q, r = divmod(13, 5)
浮点除法	13 / 5	float(13) / 5 # Python 3: 13 / 5
数学函数	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
大整数	converted to float; use Math::BigInt to create arbitrary length integers	becomes arbitrary length integer of type long
大浮点数	inf	raises OverflowError
随机数	int(rand() * 100) rand() none	import random random.randint(0,99) random.random() random.gauss(0,1)
随机数	srand 17; my $sd = srand; srand($sd);	import random random.seed(17) sd = random.getstate() random.setstate(sd)
位操作	<< >> & | ^ ~	<< >> & | ^ ~
其他进制	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
转义	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
变量替换	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	‘’’ ‘’’
字符串连接	my $s = "Hello, "; my $s2 = $s . "World!";	s = 'Hello, ' s2 = s + 'World!' juxtaposition can be used to concatenate literals: s2 = 'Hello, ' "World!"
字符串复制	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')
字符串连接	join(" ", qw(do re mi fa))	' '.join(['do', 're', 'mi', 'fa'])
字符串大小写	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)
字符串长度	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]
访问字符串中字母	can't use index notation with strings: substr("lorem ipsum", 6, 1)	'lorem ipsum'[6]
字母数字转化	chr(65) ord("A")	chr(65) ord('A')
正则表达式
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
正则表达式匹配	if ($s =~ /1999/) { print "party!\n"; }	if re.search('1999', s): print('party!')
忽略大小写	"Lorem" =~ /lorem/i	re.search('lorem', 'Lorem', re.I)
选项	i m s p x	re.I re.M re.S re.X
替换	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')
日期时间
日期时间类型	Time::Piece if use Time::Piece in effect, otherwise tm array	datetime.datetime
当前日期时间	use Time::Piece; my $t = localtime(time); my $utc = gmtime(time);	import datetime t = datetime.datetime.now() utc = datetime.datetime.utcnow()
与epoch转化	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)
当前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')
默认格式	Tue Aug 23 19:35:19 2011	2011-08-23 19:35:59.411135
字符串转为时间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)
时间差	Time::Seconds object if use Time::Piece in effect; not meaningful to subtract tm arrays	datetime.timedelta object
时间运算	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
时区	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; 是否夏令时	# 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)
数组
定义	@a = (1, 2, 3, 4);	a = [1, 2, 3, 4]
quote words	@a = qw(do re mi);	none
长度	$#a + 1 or scalar(@a)	len(a)
空测试	!@a	not a
使用	$a[0]	a[0]
更新	$a[0] = "lorem";	a[0] = 'lorem'
越界访问	@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')
子数组	select 3rd and 4th elements: @a[2..3] splice(@a, 2, 2)	select 3rd and 4th elements: a[2:4] none
子数组	@a[1..$#a]	a[1:]
添加删除	@a = (6,7,8); push @a, 9; pop @a;	a = [6,7,8] a.append(9) a.pop()
插入删除	@a = (6,7,8); unshift @a, 5; shift @a;	a = [6,7,8] a.insert(0,5) a.pop(0)
数组连接	@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)]
浅拷贝深拷贝	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)
数组作为函数参数	each element passed as separate argument; use reference to pass array as single argument	parameter contains address copy
遍历	for $i (1, 2, 3) { print "$i\n" }	for i in [1,2,3]: print(i)
遍历	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 $i (1..1_000_000) { code }	range replaces xrange in Python 3: for i in xrange(1, 1000001): code
range数组	@a = 1..10;	a = range(1, 11) Python 3: a = list(range(1, 11))
翻转	@a = (1,2,3); reverse @a; @a = reverse @a;	a = [1,2,3] a[::-1] a.reverse()
排序	@a = qw(b A a B); sort @a; @a = sort @a; sort { lc($a) cmp lc($b) } @a;	a = ['b', 'A', 'a', 'B'] sorted(a) a.sort() a.sort(key=str.lower)
去重复	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))
是否存在于数组	7 ~~ @a	7 in a
集合交集		{1,2} & {2,3,4}
集合或		{1,2} | {2,3,4}
集合运算		{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'])
字典对象
定义	%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()
函数
函数申明	sub add { $_[0] + $_[1] } sub add { my ($a, $b) = @_; $a + $b; }	def add(a, b): return a+b
函数调用	add(1, 2); parens are optional: add 1, 2;	add(1, 2)
参数丢失	set to undef	raises TypeError
参数默认值	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)
变长参数	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]))
命名参数	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()
文件和输出
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"; $s;	from StringIO import StringIO f = StringIO() f.write('lorem ipsum\n') s = f.getvalue() Python 3 moved StringIO to the io module
目录操作
build pathname	use File::Spec; File::Spec->catfile("/etc", "hosts")	os.path.join('/etc', 'hosts')
dirname and basename	use File::Basename; print dirname("/etc/hosts"); print basename("/etc/hosts");	os.path.dirname('/etc/hosts') os.path.basename('/etc/hosts')
absolute pathname	use Cwd; Cwd::abs_path("..")	os.path.abspath('..')
iterate over directory by file	use File::Basename; while ( </etc/*> ) { print basename($_) . "\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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