比较perl+python

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("hin")'

$ 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) = (1,3);
# $z set to undef:
($x,2);

x,?y,?z?= 1,3
# raises ValueError:
x,?y?= 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(1,3);
max(1,3);
@a?= (1,3);
min(@a);
max(@a);

min(1,3)
max(1,3)
min([1,3])
max([1,3])

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}sn";

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',3.7)

fmt?=?'lorem {0} {1} {2}'
fmt.format('ipsum',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",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?= (1,3,4);

a?= [1,4]

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)

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?= [6,8]
a.append(9)
a.pop()

插入删除
?

@a?= (6,8);
unshift?@a,5;
shift?@a;

a?= [6,8]
a.insert(0,5)
a.pop(0)

数组连接

@a?= (1,3);
@a2?= (@a,(4,5,6));
push?@a,6);

a?= [1,3]
a2?= a + [4,6]
a.extend([4,6])

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,[3,4]);
my?$a2?= @a;
my?@a3?=?@a;
my?@a4?= @{dclone(@a)};

import?copy

a?= [1,4]]
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?$i?(1,3) {?print?"$in"?}

for?i?in?[1,3]:
??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',?'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?= (1,3);
reverse?@a;
@a?=?reverse?@a;

a?= [1,3]
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?= (1,3);
my?@a2?= uniq?@a;
@a?= uniq?@a;

a?= [1,3]
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} & {2,4}

集合或
?

{1,2} | {2,4}

集合运算

{1,3} - {2}
{1,2} ^ {2,4}

map
?

map?{ $_ * $_ } (1,3)

map(lambda?x: x * x,[1,3])
# or use list comprehension:
[x*x for x in [1,3]]

filter
?

grep?{ $_ > 1 } (1,3)

filter(lambda?x: x > 1,3])
# or use list comprehension:
[x for x in [1,3] if x > 1]

reduce
?

use?List::Util?'reduce';

reduce { $x + $y } 0,(1,3)

# import needed in Python 3 only
from?functools?import reduce

reduce(lambda?x,y: x+y,3],0)

All/any
?

# cpan -i List::MoreUtils
use?List::MoreUtils?qw(all any);

all { $_ % 2 == 0 } (1,4)
any { $_ % 2 == 0 } (1,4)

all(i%2 == 0?for?i?in?[1,4])
any(i%2 == 0?for?i?in?[1,4])

shuffle and sample

use?List::Util?'shuffle';

@a?= (1,4);
shuffle(@a);
none

from?random?import?shuffle,sample

a?= [1,4]
shuffle(a)
sample(a,2)

zip
?

# cpan -i List::MoreUtils
use?List::MoreUtils?'zip';

@nums?= (1,3);
@lets?=?qw(a b c);
# flat array of 6 elements:
@a?= zip?@nums,?@lets;

# array of 3 pairs:
a?= zip([1,['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","b","c");
%d?=?@a;

a?= [[1,'a'],[2,'b'],'c']]
d?=?dict(a)

a?= [1,'a','b','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?= (1,3);
my?%d?= ("t"=> 1,?"f"?=> 0);
foo(@a,%d);

def?foo(x,y):
??x[2] = 5
??y['f'] = -1

a?= [1,3]
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?= (1,3);
($x,$y) = first_and_second(@a);

def?first_and_second(a):
??return?a[0],a[1]

x,?y?= first_and_second([1,3])

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 hitsn"
}?elsif?( 1 == $n ) {
??print?"one hitn"
}?else?{
??print?"$n hitsn"
}

if?0 == n:
??print('no hits')
elif?1 == n:
??print('one hit')
else:
??print(str(n) +?' hits')

switch

use?feature?'switch';

given ($n) {
??when (0) {?print?"no hitsn"; }
??when (1) {?print?"one hitn"; }
??default {?print?"$n hitsn"; }
}

none

while
?

while?( $i < 100 ) { $i++ }

while?i < 100:
??i += 1

c-style for
?

for?( $i=0; $i <= 10; $i++ ) {
??print?"$in";
}

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 [1,3]:

? 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?"positiven"?if?$i > 0;
print?"nonzeron"?unless?$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 ipsumn')

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('rn')

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 ipsumn";
close $f;

print?"tmp file: ";
print?$f->filename .?"n";

import?tempfile

f?= tempfile.NamedTemporaryFile(
??prefix='foo')
f.write('lorem ipsumn')
f.close()

print("tmp file: %s"?% f.name)

in memory file

my?($f,?$s);
open($f,?">",$s);
print?$f?"lorem ipsumn";
$s;

from?StringIO?import?StringIO

f?= StringIO()
f.write('lorem ipsumn')
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 SRCn";
??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',?'/tmp']
files?= subprocess.check_output(cmd)

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