|
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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