| ? |
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) |
| __________________________________________ |
