1 一行赋值序列和元组
|
1
2
3
4
5
6
|
In [
11
]: l
=
[
'a'
,
'b'
]
In [
12
]: x,y
=
l
In [
13
]: x
Out[
13
]:
'a'
In [
14
]: y
Out[
14
]:
'b'
|
|
1
2
3
4
5
6
|
In [
15
]: t
=
(
1
,
2
)
In [
16
]: m,n
=
t
In [
17
]: m
Out[
17
]:
1
In [
18
]: n
Out[
18
]:
2
|
2 交换变量
|
1
2
3
4
5
6
7
|
In [
6
]: m
=
3
In [
7
]: n
=
4
In [
8
]: m,n
=
n,m
In [
9
]: m
Out[
9
]:
4
In [
10
]: n
Out[
10
]:
3
|
3 语句在行内，if 的三目运算
|
1
2
|
In [
19
]:
print
'Hello'
if
True
else
'World'
Hello
|
|
1
2
3
4
5
6
7
|
In [
20
]: a
=
' ni'
In [
21
]: b
=
a.strip()
if
a.strip()
else
None
In [
22
]: b
Out[
22
]:
'ni'
In [
23
]: a
=
' '
In [
24
]: b
=
a.strip()
if
a.strip()
else
None
In [
25
]: b
|
4 连接--相同类型的数据可以连接拼接
|
1
2
3
4
|
In [
27
]: s
=
'my name is: '
In [
28
]: msg
=
s
+
'Andy'
In [
29
]: msg
Out[
29
]:
'my name is: Andy'
|
|
1
2
3
4
|
In [
30
]: l1
=
[
'Apple'
,
'orange'
]
In [
31
]: l2
=
[
'Banana'
,
'Grape'
]
In [
32
]: l1
+
l2
Out[
32
]: [
'Apple'
,
'orange'
,
'Banana'
,
'Grape'
]
|
5 数字技巧
整数和浮点除
|
1
2
3
4
|
In [
33
]:
5
/
2
Out[
33
]:
2
In [
34
]:
5.0
/
2
Out[
34
]:
2.5
|
整数和浮点取余数
|
1
2
3
4
|
In [
36
]:
5
%
2
Out[
36
]:
1
In [
37
]:
5.00
%
2
Out[
37
]:
1.0
|
6 数字比较和少语言可以如此用法
|
1
2
3
4
|
In [
43
]:
if
x <
5
and
x >
2
:
....:
print
x
....:
3
|
等于
|
1
2
3
4
|
In [
44
]:
if
2
< x <
5
:
....:
print
x
....:
3
|
7 同时迭代两个列表(序列)
|
1
2
3
4
5
6
7
8
9
|
In [
46
]: l1
Out[
46
]: [
'Apple'
,
'orange'
]
In [
47
]: l2
Out[
47
]: [
'Banana'
,
'Grape'
]
In [
48
]:
for
item1, item2
in
zip
(l1, l2):
....:
print
item1
+
' vs '
+
item2
....:
Apple vs Banana
orange vs Grape
|
8 带索引的列表迭代
|
1
2
3
4
5
|
In [
51
]:
for
index, item
in
enumerate
(l1):
....:
print
index, item
....:
0
Apple
1
orange
|
|
1
2
3
4
5
|
In [
52
]:
for
index, item
in
enumerate
(l1):
....:
print
index
+
1
, item
....:
1
Apple
2
orange
|
9 生成列表(列表推到式)
|
1
2
3
4
5
6
7
8
|
In [
53
]: numbers
=
[
1
,
2
,
3
,
4
,
5
,
6
,
7
,
8
]
In [
54
]: even
=
[]
In [
55
]:
for
number
in
numbers:
....:
if
number
%
2
=
=
0
:
....: even.append(number)
....:
In [
56
]: even
Out[
56
]: [
2
,
4
,
6
,
8
]
|
等价于一行语句
|
1
2
3
|
In [
59
]: even
=
[ number
for
number
in
numbers
if
number
%
2
=
=
0
]
In [
60
]: even
Out[
60
]: [
2
,
4
,
6
,
8
]
|
10 字典推导(只使用 python 2.7版本 不适合以下版本)
|
1
2
3
4
|
names
=
[
'andy'
,
'jack'
,
'tom'
,
'john'
]
d
=
{key: value
for
value, key
in
enumerate
(names)}
>>> d
{
'john'
:
3
,
'andy'
:
0
,
'jack'
:
1
,
'tom'
:
2
}
|
11 列表转字符串
|
1
2
3
4
|
In [
64
]: l1
Out[
64
]: [
'Apple'
,
'orange'
]
In [
66
]:
","
.join(l1)
Out[
66
]:
'Apple,orange'
|
12 字符串转列表
|
1
2
3
|
In [
67
]: ids
=
"4,57,9,22,31"
In [
68
]: ids.split(
','
)
Out[
68
]: [
'4'
,
'57'
,
'9'
,
'22'
,
'31'
]
|
13获取列表的子集(切片)
|
1
|
In [
2
]: x
=
[
1
,
2
,
3
,
4
,
5
,
6
]
|
获取前三个
|
1
2
|
In [
3
]: x[:
3
]
Out[
3
]: [
1
,
2
,
3
]
|
获取index=0 到 index=4的
|
1
2
|
In [
4
]: x[
1
:
5
]
Out[
4
]: [
2
,
3
,
4
,
5
]
|
获取后面3个
|
1
2
|
In [
5
]: x[
-
3
:]
Out[
5
]: [
4
,
5
,
6
]
|
获取奇数(从第一个到最后一个，步长为2)
|
1
2
|
In [
6
]: x[::
2
]
Out[
6
]: [
1
,
3
,
5
]
|
获取偶数(从第一个到最后一个，步长为2)
|
1
2
|
In [
7
]: x[
1
::
2
]
Out[
7
]: [
2
,
4
,
6
]
|
倒序
|
1
2
|
In [
8
]: x[::
-
1
]
Out[
8
]: [
6
,
5
,
4
,
3
,
2
,
1
]
|
14 合并列表zip
n个列表通过zip函数后，返回一个n个元素组成的元组形式的列表(列表长度为最短的那个列表)
|
1
2
3
4
5
6
|
In [
23
]: l1
Out[
23
]: [
1
,
2
,
3
,
4
]
In [
24
]: l2
Out[
24
]: [
6
,
7
,
8
,
9
]
In [
25
]:
zip
(l1,l2)
Out[
25
]: [(
1
,
6
), (
2
,
7
), (
3
,
8
), (
4
,
9
)]
|
|
1
2
|
In [
17
]: [x
+
y
for
x,y
in
zip
(l1,l2)]
Out[
17
]: [
7
,
9
,
11
,
13
]
|
15 序列的映射map
map(function, sequence[, sequence, ...]) -> list
多个序列通过function返回后返回一个新的列表，最好是序列的长度要一致(不一致的元素补None)
function 可以为None，那么map功能就和zip一样了
|
1
2
|
In [
27
]:
map
(
None
,l1,l2)
Out[
27
]: [(
1
,
6
), (
2
,
7
), (
3
,
8
), (
4
,
9
)]
|
|
1
2
|
In [
28
]:
map
(
lambda
x,y:x
+
y , l1,l2)
Out[
28
]: [
7
,
9
,
11
,
13
]
|
16 插入一条常见知识，程序中出现中文执行程序报错
syntaxError: Non-ASCII character '\xe4' in file test.py on line 7
解决:
|
1
2
3
4
5
|
#!/usr/bin/env python
#encoding=utf-8
import
sys
reload
(sys)
sys.setdefaultencoding(
'utf-8'
)
|
以上格式肯定是不会出错，注意#encoding=utf-8 一定要在第二行，在其他行不起作用
17 可以定义一个python执行错误的函数，每次执行错误，调用即可
#python 参数输入错误的提示输入函数
|
1
2
3
4
|
def
exec_error(msg
=
None
):
print
"\
033
[
1
;
31
;
40mUsage
: python xxx.py {
0
|
1
|
2
|
3
|
all
}\
033
[
0m
\n\t \
0
:
None
level project,
1
:level
1
project,
2
:level
2
project,
3
:level
3
project,
all
:
all
project"
sys.exit()
|
18 通过ip地址翻译的主机名的函数
#通过ip或者hostname解析获得hostname,ip
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
|
def
resolve_host(s):
l
=
s.split(
'.'
)
if
len
(l) >
4
:
return
"-"
if
len
(l)
=
=
4
:
ip
=
s
try
:
hostname
=
socket.gethostbyaddr(s)[
0
]
except
Exception,e:
#print "could't look up name by ipaddress:",e
#sys.exit(1)
return
'-'
else
:
return
'-'
return
hostname
|
19 filter函数
python自带
常用过滤列表
用法: filter(函数,列表)
递归传递列表的值到函数中函数返回值为true则作为新列表的元素
|
1
2
3
|
In [
7
]: l
=
[
1
,
2
,
3
,
4
,
5
]
In [
8
]:
filter
(
lambda
x : x >
3
, l)
Out[
8
]: [
4
,
5
]
|
其实等价于 和生成序列的常用方法效果一样
|
1
|
[i
for
i
in
l
if
i >
3
]
|
实践中的用途:
|
1
2
3
4
|
In [
19
]: task_id
=
4
In [
20
]: tasks
=
[{
"id"
:
3
,
"title"
:
"three"
}, {
"id"
:
4
,
"title"
:
"four"
}, {
"id"
:
5
,
"title"
:
"five"
}]
In [
21
]:
filter
(
lambda
i: i[
"id"
]
=
=
task_id ,tasks)
Out[
21
]: [{
'id'
:
4
,
'title'
:
'four'
}]
|
本文转自残剑博客51CTO博客，原文链接http://blog.51cto.com/cuidehua/1768413如需转载请自行联系原作者
cuizhiliang
