这个题可以这样实现:
[code lang="pyton"]
f= open('sss','r').readlines()
f[100:300]
文件并不能直接进行切片操作。redlines()可以把每一行读入到一个列表中。
弊端，readlines()方法会一次性的把文件导入到内存当中，如果文件很大，那就尴尬了（内存不足）。
我们可以使用标准库下的itertools下的islice 方法
In [74]: from <span class="wp_keywordlink_affiliate"><a href="https://www.168seo.cn/tag/itertools" title="View all posts in itertools" target="_blank">itertools</a></span> import <span class="wp_keywordlink_affiliate"><a href="https://www.168seo.cn/tag/islice" title="View all posts in islice" target="_blank">islice</a></span> In [75]: <span class="wp_keywordlink_affiliate"><a href="https://www.168seo.cn/tag/islice" title="View all posts in islice" target="_blank">islice</a></span>? Init signature: islice(self, /, *args, **kwargs) Docstring: islice(iterable, stop) --> islice object islice(iterable, start, stop[, step]) --> islice object Return an iterator whose next() method returns selected values from an iterable. If start is specified, will skip all preceding elements; otherwise, start defaults to zero. Step defaults to one. If specified as another value, step determines how many values are skipped between successive calls. Works like a slice() on a list but returns an iterator. Type: type In [76]: islice(f,0,10) Out[76]: <<span class="wp_keywordlink_affiliate"><a href="https://www.168seo.cn/tag/itertools" title="View all posts in itertools" target="_blank">itertools</a></span>.islice at 0x1055fe638> # 读取前十行 In [77]: islice(f,0,None) Out[77]: <<span class="wp_keywordlink_affiliate"><a href="https://www.168seo.cn/tag/itertools" title="View all posts in itertools" target="_blank">itertools</a></span>.islice at 0x1056014f8> # 从开头带结尾 In [78]: islice(f,10) Out[78]: <itertools.islice at 0x1055ae868> # 读取前十行 In [85]: l Out[85]: range(0, 10) In [86]: t = iter(l) In [87]: for x in islice(t,5,7): ...: print(x) ...: 5 6 #注意如果在用到迭代器,他会直接往下走,所以要用的时候注意下,你可以重新iter一个,这样就不会有问题了 In [88]: for x in t: ...: print(x) ...: ...: 7 8 9
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In
[
74
]
:
from
itertools
import
islice
In
[
75
]
:
islice
?
Init
signature
:
islice
(
self
,
/
,
*
args
,
*
*
kwargs
)
Docstring
:
islice
(
iterable
,
stop
)
--
>
islice
object
islice
(
iterable
,
start
,
stop
[
,
step
]
)
--
>
islice
object
Return
an
iterator
whose
next
(
)
method
returns
selected
values
from
an
iterable
.
If
start
is
specified
,
will
skip
all
preceding
elements
;
otherwise
,
start
defaults
to
zero
.
Step
defaults
to
one
.
If
specified
as
another
value
,
step
determines
how
many
values
are
skipped
between
successive
calls
.
Works
like
a
slice
(
)
on
a
list
but
returns
an
iterator
.
Type
:
type
In
[
76
]
:
islice
(
f
,
0
,
10
)
Out
[
76
]
:
<
itertools
.
islice
at
0x1055fe638
>
# 读取前十行
In
[
77
]
:
islice
(
f
,
0
,
None
)
Out
[
77
]
:
<
itertools
.
islice
at
0x1056014f8
>
# 从开头带结尾
In
[
78
]
:
islice
(
f
,
10
)
Out
[
78
]
:
<
itertools
.
islice
at
0x1055ae868
>
# 读取前十行
In
[
85
]
:
l
Out
[
85
]
:
range
(
0
,
10
)
In
[
86
]
:
t
=
iter
(
l
)
In
[
87
]
:
for
x
in
islice
(
t
,
5
,
7
)
:
.
.
.
:
print
(
x
)
.
.
.
:
5
6
#注意如果在用到迭代器,他会直接往下走,所以要用的时候注意下,你可以重新iter一个,这样就不会有问题了
In
[
88
]
:
for
x
in
t
:
.
.
.
:
print
(
x
)
.
.
.
:
.
.
.
:
7
8
9
|
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