File io 如何在Julia中逐行读取文件?
如何打开文本文件并逐行读取?我对以下两种不同的情况感兴趣:File io 如何在Julia中逐行读取文件?,file-io,julia,File Io,Julia,如何打开文本文件并逐行读取?我对以下两种不同的情况感兴趣: 一次获取数组中的所有行 一次处理一行 对于第二种情况,我不希望一次将所有行保存在内存中。将一个文件作为一个行数组一次全部读入内存只需调用readlines函数: julia> words = readlines("/usr/share/dict/words") 235886-element Array{String,1}: "A" "a" "aa" ⋮ "zythum" "Zyzomys" "Zyzzogeton"
对于第二种情况,我不希望一次将所有行保存在内存中。将一个文件作为一个行数组一次全部读入内存只需调用
readlines
函数:
julia> words = readlines("/usr/share/dict/words")
235886-element Array{String,1}:
"A"
"a"
"aa"
⋮
"zythum"
"Zyzomys"
"Zyzzogeton"
julia> open("/usr/share/dict/words") do io
readline(io) # throw out the first line
readlines(io)
end
235885-element Array{String,1}:
"a"
"aa"
"aal"
⋮
"zythum"
"Zyzomys"
"Zyzzogeton"
默认情况下,这将丢弃换行符,但如果要保留它们,可以传递关键字参数keep=true
:
julia> words = readlines("/usr/share/dict/words", keep=true)
235886-element Array{String,1}:
"A\n"
"a\n"
"aa\n"
⋮
"zythum\n"
"Zyzomys\n"
"Zyzzogeton\n"
如果已经打开了文件对象,也可以将其传递给readlines
函数:
julia> words = readlines("/usr/share/dict/words")
235886-element Array{String,1}:
"A"
"a"
"aa"
⋮
"zythum"
"Zyzomys"
"Zyzzogeton"
julia> open("/usr/share/dict/words") do io
readline(io) # throw out the first line
readlines(io)
end
235885-element Array{String,1}:
"a"
"aa"
"aal"
⋮
"zythum"
"Zyzomys"
"Zyzzogeton"
这演示了readline
函数,该函数从打开的I/O对象中读取一行,或者在给定文件名时,打开文件并从中读取第一行:
julia> readline("/usr/share/dict/words")
"A"
如果您不想一次加载所有文件内容(或者如果您正在处理来自网络套接字的流式数据),则可以使用eachline
函数获取迭代器,该迭代器一次生成一行:
julia> for word in eachline("/usr/share/dict/words")
if length(word) >= 24
println(word)
end
end
formaldehydesulphoxylate
pathologicopsychological
scientificophilosophical
tetraiodophenolphthalein
thyroparathyroidectomize
eachline
函数也可以像readlines
一样,被赋予一个打开的文件句柄以从中读取行。您也可以通过打开文件并反复调用readline
来“滚动您自己的”迭代器:
julia> open("/usr/share/dict/words") do io
while !eof(io)
word = readline(io)
if length(word) >= 24
println(word)
end
end
end
formaldehydesulphoxylate
pathologicopsychological
scientificophilosophical
tetraiodophenolphthalein
thyroparathyroidectomize
这相当于eachline
为您所做的事情,您很少需要自己做这件事,但如果您需要的话,这种能力就存在了。有关逐个字符读取文件的详细信息,请参阅此问题和答案: