比较perl+python的优点和缺点

时间：2022-03-05 17:35:54

 

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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