| | 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) |
__________________________________________ |
2017-10-05 11:03:57 
阿炯