Julia:将数字字符串转换为float或int

Question

我正在尝试将从数据库中提取的数字数据写入Float64[].原始数据是::ASCIIString格式化的,因此尝试将其推送到数组会出现以下错误:

julia> push!(a, "1")
ERROR: MethodError: `convert` has no method matching convert(::Type{Float64}, ::ASCIIString)
This may have arisen from a call to the constructor Float64(...),
since type constructors fall back to convert methods.
Closest candidates are:
  call{T}(::Type{T}, ::Any)
  convert(::Type{Float64}, ::Int8)
  convert(::Type{Float64}, ::Int16)
  ...
 in push! at array.jl:432

试图直接转换数据不出所料引发同样的错误:

julia> convert(Float64, "1")
ERROR: MethodError: `convert` has no method matching convert(::Type{Float64}, ::ASCIIString)
This may have arisen from a call to the constructor Float64(...),
since type constructors fall back to convert methods.
Closest candidates are:
  call{T}(::Type{T}, ::Any)
  convert(::Type{Float64}, ::Int8)
  convert(::Type{Float64}, ::Int16)
  ...

鉴于我知道数据是数字的,有没有办法在推送之前将其转换？

ps我使用的是0.4.0版本

Answer 1

你可以parse(Float64,"1")从一个字符串.或者在矢量的情况下

map(x->parse(Float64,x),stringvec)

将解析整个向量.

BTW考虑使用tryparse(Float64,x)而不是解析.它返回一个Nullable {Float64},在字符串不能很好地解析的情况下为null.例如:

isnull(tryparse(Float64,"33.2.1")) == true

并且通常在解析错误的情况下需要默认值:

strvec = ["1.2","NA","-1e3"]
map(x->(v = tryparse(Float64,x); isnull(v) ? 0.0 : get(v)),strvec)
# gives [1.2,0.0,-1000.0]

Answer 2

使用parse(Float64,"1").

请参阅:解析规范