使用sys重定向输出
import
sys
import
string
class
Redirect:
def
_ _init_ _(
self
, stdout):
self
.stdout
=
stdout
def
write(
self
, s):
self
.stdout.write(string.lower(s))
# redirect standard output (including the print statement)
# 重定向标准输出(包括print语句)
old_stdout
=
sys.stdout
sys.stdout
=
Redirect(sys.stdout)
print
"HEJA SVERIGE"
,
print
"FRISKT HUM\303\226R"
# restore standard output
# 恢复标准输出
sys.stdout
=
old_stdout
print
"M\303\205\303\205\303\205\303\205L!"
heja sverige friskt hum\
303
\
266r
M\
303
\
205
\
303
\
205
\
303
\
205
\
303
\
205L
!
|
使用sys模块退出程序
import
sys
print
"hello"
sys.exit(
1
)
print
"there"
hello
|
注意 sys.exit 并不是立即退出. 而是引发一个 SystemExit 异常. 这意味着你可以在主程序中捕获对 sys.exit 的调用
捕获sys.exit调用
import
sys
print
"hello"
try
:
sys.exit(
1
)
except
SystemExit:
pass
print
"there"
hello
there
|
如果准备在退出前自己清理一些东西(比如删除临时文件), 你可以配置一个 "退出处理函数"(exit handler), 它将在程序退出的时候自动被调用
另一种捕获sys.exit调用的方法
import
sys
def
exitfunc():
print
"world"
sys.exitfunc
=
exitfunc
print
"hello"
sys.exit(
1
)
print
"there"
# never printed # 不会被 print
hello
world
|
在 Python 2.0 以后, 你可以使用 atexit 模块来注册多个退出处理函数.
atexit 模块允许你注册一个或多个终止函数(暂且这么叫), 这些函数将在解释器终止前被自动调用.
调用 register 函数, 便可以将函数注册为终止函数,你也可以添加更多的参数, 这些将作为 exit 函数的参数传递.
使用 atexit 模块
import
atexit
def
exit(
*
args):
print
"exit"
, args
# register two exit handler
atexit.register(exit)
atexit.register(exit,
1
)
atexit.register(exit,
"hello"
,
"world"
)
exit (
'hello'
,
'world'
)
exit (
1
,)
exit ()
|
time 模块提供了一些处理日期和一天内时间的函数. 它是建立在 C 运行时库的简单封装.
给定的日期和时间可以被表示为浮点型(从参考时间, 通常是 1970.1.1 到现在经过的秒数. 即 Unix 格式), 或者一个表示时间的 struct (类元组).
使用 time 模块获取当前时间
import
time
now
=
time.time()
print
now,
"seconds since"
, time.gmtime(
0
)[:
6
]
print
print
"or in other words:"
print
"- local time:"
, time.localtime(now)
print
"- utc:"
, time.gmtime(now)
937758359.77
seconds since (
1970
,
1
,
1
,
0
,
0
,
0
)
or
in
other words:
-
local time: (
1999
,
9
,
19
,
18
,
25
,
59
,
6
,
262
,
1
)
-
utc: (
1999
,
9
,
19
,
16
,
25
,
59
,
6
,
262
,
0
)
|
使用 time 模块格式化时间输出
import
time
now
=
time.localtime(time.time())
print
time.asctime(now)
print
time.strftime(
"%y/%m/%d %H:%M"
, now)
print
time.strftime(
"%a %b %d"
, now)
print
time.strftime(
"%c"
, now)
print
time.strftime(
"%I %p"
, now)
print
time.strftime(
"%Y-%m-%d %H:%M:%S %Z"
, now)
# do it by hand...
year, month, day, hour, minute, second, weekday, yearday, daylight
=
now
print
"%04d-%02d-%02d"
%
(year, month, day)
print
"%02d:%02d:%02d"
%
(hour, minute, second)
print
(
"MON"
,
"TUE"
,
"WED"
,
"THU"
,
"FRI"
,
"SAT"
,
"SUN"
)[weekday], yearday
Sun
Oct
10
21
:
39
:
24
1999
99
/
10
/
10
21
:
39
Sun
Oct
10
Sun
Oct
10
21
:
39
:
24
1999
09
PM
1999
-
10
-
10
21
:
39
:
24
CEST
1999
-
10
-
10
21
:
39
:
24
SUN
283
|
在一些平台上, time 模块包含了 strptime 函数, 它的作用与 strftime 相反. 给定一个字符串和模式, 它返回相应的时间对象
使用 time.strptime 函数解析时间
import
time
# make sure we have a strptime function!
# 确认有函数 strptime
try
:
strptime
=
time.strptime
except
AttributeError:
from
strptime
import
strptime
print
strptime(
"31 Nov 00"
,
"%d %b %y"
)
print
strptime(
"1 Jan 70 1:30pm"
,
"%d %b %y %I:%M%p"
)
|
strptime 不完全实现
import
re
import
string
MONTHS
=
[
"Jan"
,
"Feb"
,
"Mar"
,
"Apr"
,
"May"
,
"Jun"
,
"Jul"
,
"Aug"
,
"Sep"
,
"Oct"
,
"Nov"
,
"Dec"
]
SPEC
=
{
# map formatting code to a regular expression fragment
"%a"
:
"(?P<weekday>[a-z]+)"
,
"%A"
:
"(?P<weekday>[a-z]+)"
,
"%b"
:
"(?P<month>[a-z]+)"
,
"%B"
:
"(?P<month>[a-z]+)"
,
"%C"
:
"(?P<century>\d\d?)"
,
"%d"
:
"(?P<day>\d\d?)"
,
"%D"
:
"(?P<month>\d\d?)/(?P<day>\d\d?)/(?P<year>\d\d)"
,
"%e"
:
"(?P<day>\d\d?)"
,
"%h"
:
"(?P<month>[a-z]+)"
,
"%H"
:
"(?P<hour>\d\d?)"
,
"%I"
:
"(?P<hour12>\d\d?)"
,
"%j"
:
"(?P<yearday>\d\d?\d?)"
,
"%m"
:
"(?P<month>\d\d?)"
,
"%M"
:
"(?P<minute>\d\d?)"
,
"%p"
:
"(?P<ampm12>am|pm)"
,
"%R"
:
"(?P<hour>\d\d?):(?P<minute>\d\d?)"
,
"%S"
:
"(?P<second>\d\d?)"
,
"%T"
:
"(?P<hour>\d\d?):(?P<minute>\d\d?):(?P<second>\d\d?)"
,
"%U"
:
"(?P<week>\d\d)"
,
"%w"
:
"(?P<weekday>\d)"
,
"%W"
:
"(?P<weekday>\d\d)"
,
"%y"
:
"(?P<year>\d\d)"
,
"%Y"
:
"(?P<year>\d\d\d\d)"
,
"%%"
:
"%"
}
class
TimeParser:
def
_ _init_ _(
self
,
format
):
# convert strptime format string to regular expression
format
=
string.join(re.split(
"(?:\s|%t|%n)+"
,
format
))
pattern
=
[]
try
:
for
spec
in
re.findall(
"%\w|%%|."
,
format
):
if
spec[
0
]
=
=
"%"
:
spec
=
SPEC[spec]
pattern.append(spec)
except
KeyError:
raise
ValueError,
"unknown specificer: %s"
%
spec
self
.pattern
=
re.
compile
(
"(?i)"
+
string.join(pattern, ""))
def
match(
self
, daytime):
# match time string
match
=
self
.pattern.match(daytime)
if
not
match:
raise
ValueError,
"format mismatch"
get
=
match.groupdict().get
tm
=
[
0
]
*
9
# extract date elements
y
=
get(
"year"
)
if
y:
y
=
int
(y)
if
y <
68
:
y
=
2000
+
y
elif
y <
100
:
y
=
1900
+
y
tm[
0
]
=
y
m
=
get(
"month"
)
if
m:
if
m
in
MONTHS:
m
=
MONTHS.index(m)
+
1
tm[
1
]
=
int
(m)
d
=
get(
"day"
)
if
d: tm[
2
]
=
int
(d)
# extract time elements
h
=
get(
"hour"
)
if
h:
tm[
3
]
=
int
(h)
else
:
h
=
get(
"hour12"
)
if
h:
h
=
int
(h)
if
string.lower(get(
"ampm12"
, "
")) == "
pm":
h
=
h
+
12
tm[
3
]
=
h
m
=
get(
"minute"
)
if
m: tm[
4
]
=
int
(m)
s
=
get(
"second"
)
if
s: tm[
5
]
=
int
(s)
# ignore weekday/yearday for now
return
tuple
(tm)
def
strptime(string,
format
=
"%a %b %d %H:%M:%S %Y"
):
return
TimeParser(
format
).match(string)
if
_ _name_ _
=
=
"_ _main_ _"
:
# try it out
import
time
print
strptime(
"2000-12-20 01:02:03"
,
"%Y-%m-%d %H:%M:%S"
)
print
strptime(time.ctime(time.time()))
(
2000
,
12
,
20
,
1
,
2
,
3
,
0
,
0
,
0
)
(
2000
,
11
,
15
,
12
,
30
,
45
,
0
,
0
,
0
)
|
使用 time 模块将本地时间元组转换为时间值(整数)
import
time
t0
=
time.time()
tm
=
time.localtime(t0)
print
tm
print
t0
print
time.mktime(tm)
(
1999
,
9
,
9
,
0
,
11
,
8
,
3
,
252
,
1
)
936828668.16
936828668.0
|
将 UTC 时间元组转换为时间值(整数)
import
time
def
_d(y, m, d, days
=
(
0
,
31
,
59
,
90
,
120
,
151
,
181
,
212
,
243
,
273
,
304
,
334
,
365
)):
# map a date to the number of days from a reference point
return
(((y
-
1901
)
*
1461
)
/
4
+
days[m
-
1
]
+
d
+
((m >
2
and
not
y
%
4
and
(y
%
100
or
not
y
%
400
))
and
1
))
def
timegm(tm, epoch
=
_d(
1970
,
1
,
1
)):
year, month, day, h, m, s
=
tm[:
6
]
assert
year >
=
1970
assert
1
<
=
month <
=
12
return
(_d(year, month, day)
-
epoch)
*
86400
+
h
*
3600
+
m
*
60
+
s
t0
=
time.time()
tm
=
time.gmtime(t0)
print
tm
print
t0
print
timegm(tm)
(
1999
,
9
,
8
,
22
,
12
,
12
,
2
,
251
,
0
)
936828732.48
936828732
|
使用 time 模块评价算法
import
time
def
procedure():
time.sleep(
2.5
)
# measure process time
t0
=
time.clock()
procedure()
print
time.clock()
-
t0,
"seconds process time"
# measure wall time
t0
=
time.time()
procedure()
print
time.time()
-
t0,
"seconds wall time"
0.0
seconds process time
2.50903499126
seconds wall time
|
使用 types 模块
import
types
def
check(
object
):
print
object
,
if
type
(
object
)
is
types.IntType:
print
"INTEGER"
,
if
type
(
object
)
is
types.FloatType:
print
"FLOAT"
,
if
type
(
object
)
is
types.StringType:
print
"STRING"
,
if
type
(
object
)
is
types.ClassType:
print
"CLASS"
,
if
type
(
object
)
is
types.InstanceType:
print
"INSTANCE"
,
print
check(
0
)
check(
0.0
)
check(
"0"
)
class
A:
pass
class
B:
pass
check(A)
check(B)
a
=
A()
b
=
B()
check(a)
check(b)
0
INTEGER
0.0
FLOAT
0
STRING
A CLASS
B CLASS
<A instance at
796960
> INSTANCE
<B instance at
796990
> INSTANCE
|
使用 gc 模块收集循环引用垃圾
import
gc
# create a simple object that links to itself
class
Node:
def
_ _init_ _(
self
, name):
self
.name
=
name
self
.parent
=
None
self
.children
=
[]
def
addchild(
self
, node):
node.parent
=
self
self
.children.append(node)
def
_ _repr_ _(
self
):
return
"<Node %s at %x>"
%
(
repr
(
self
.name),
id
(
self
))
# set up a self-referencing structure
root
=
Node(
"monty"
)
root.addchild(Node(
"eric"
))
root.addchild(Node(
"john"
))
root.addchild(Node(
"michael"
))
# remove our only reference
del
root
print
gc.collect(),
"unreachable objects"
print
gc.collect(),
"unreachable objects"
12
unreachable objects
0
unreachable objects
|
