`string(dict)` loses information

General Usage
1

string(dict) loses information if dict contains Float64. How to avoid this behavior?

# on v1.0
x = 1.000000101e8 # Float64
y = 2.000000202e8 # Float64

d = Dict("x"=>x, "y"=>y)
d2 = eval(Meta.parse(string(d)))

d["x"] == d2["x"] # false
2

Dont assume that you can get back your data from an object by parsing the output of string on it.

1 Like
3

There seems to be context option in sprint.

x = 1.000000101e8
y = 2.000000202e8

d = Dict("x"=>x, "y"=>y)
d2 = eval(Meta.parse(string(d)))
d3 = eval(Meta.parse(sprint(show, d, context=:compact => false)))

d["x"] == d2["x"] # false
d["x"] == d3["x"] # true
4

Dictionary printing probably shouldn’t pass :compact by default. We don’t do that in vectors or single-column matrices anymore and it elf masker sense for Dict printing to match. But yes, in general, you can’t assume that object printing preserves all information.

5

Indeed one shouldn’t rely on that for string. which is just “give me a string at represents this in some way”.

I feel like we should be able to rely on it for repr.
I think we should have have python’s convention,
which is roughly: if it parses, then evaling it should give back the same as a deep copy.

But we did not adopt that convention, and it is a breaking change.
So you can not

6

A pointed out above, printing is not guaranteed to preserve information. If you are trying to save data, consider

or serialization.