Format a text in GO better then fmt
Looking at the article title, we should clarify what means better and what is text formatting. Lets start from the last one from these these theses. Text formatting is an important part of programming, prepared text is using in a various tasks:
- description/result of some operations;
- detailed log;
- as a query for data selection in other systems;
- and in many others fields.
Better means that
sf
(wissance.StringFormatter) has features thatfmt
has't (see chapter 1 to see our text formatting approach).
1. What can do sf aka wissance.stringFormatter
In our earlier article we were writing about sf
convinience (convenience is a thing that is subjective to humans; here, I mean convenience based on my own background). But briefly it is more covnenient to format text like:
userNews = stringFormatter.Format("Hi \"{0}\", see latest news: {1}", "john doe", "1. You won 1M$ in a lottery, please give us your VISA/MS card data to receive money.")
then like:
userNews = fmt.Sprintf("Hi \"%s\", see latest news: %s", "john doe", "1. You won 1M$ in a lottery, please give us your VISA/MS card data to receive money.")
Until version 1.2.0
sf
was unable to make more precise argument formatting (i.e., use different number notation: bin
, hex
), starting with 1.2.0 we could do almost all that fmt
supports:
- Bin number formatting:
-
{0:B}
, 15 outputs ->1111
-
{0:B8}
, 15 outputs ->00001111
-
- Hex number formatting
-
{0:X}
, 250 outputs ->fa
-
{0:X4}
, 250 outputs ->00fa
-
- Oct number formatting
-
{0:o}
, 11 outputs ->14
-
- Float point number formatting
-
{0:E2}
, 191.0478 outputs ->1.91e+02
-
{0:F}
, 10.4567890 outputs ->10.456789
-
{0:F4}
, 10.4567890 outputs ->10.4568
-
{0:F8}
, 10.4567890 outputs ->10.45678900
-
- Percentage output
-
{0:P100}
, 12 outputs ->12%
-
sf
has 2 string format methods - Format
and FormatComplex
. Latter also allows passing argument formatting, like for Format
method.
Let's consider a minimal example:
- We should build text using the following format
"Today tempearture is {temp}, humidity is {hum}
where{temp}
and{hum}
should be replaced with an actual sensor values. - We would like to specify
{temp}
and{hum}
output, i.e.,{temp}
should have 4 digits after the dot, and{hum}
must be outputted in percents. After analyzing these requirements, we modified our template as follows:"Today tempearture is {temp:F4}, humidity is {hum:P100}"
. - Passing
12.3456
and60
like this:
sf.FormatComplex("Today tempearture is {temp:F4}, humidity is {hum:P100}", map[string]any {"temp":12.3456, "hum":60})
More examples could be found in a FormatComplex
unit test, see in repo and below:
func TestFormatComplexWithArgFormatting(t *testing.T) {
for name, test := range map[string]struct {
template string
args map[string]any
expected string
}{
"numeric_test_1": {
template: "This is the text with an only number formatting: scientific - {mass} / {mass : e2}",
args: map[string]any{"mass": 191.0784},
expected: "This is the text with an only number formatting: scientific - 191.0784 / 1.91e+02",
},
"numeric_test_2": {
template: "This is the text with an only number formatting: binary - {bin:B} / {bin : B8}, hexadecimal - {hex:X} / {hex : X4}",
args: map[string]any{"bin": 15, "hex": 250},
expected: "This is the text with an only number formatting: binary - 1111 / 00001111, hexadecimal - fa / 00fa",
},
"numeric_test_3": {
template: "This is the text with an only number formatting: decimal - {float:F} / {float : F4} / {float:F8}",
args: map[string]any{"float": 10.5467890},
expected: "This is the text with an only number formatting: decimal - 10.546789 / 10.5468 / 10.54678900",
},
} {
t.Run(name, func(t *testing.T) {
assert.Equal(t, test.expected, stringFormatter.FormatComplex(test.template, test.args))
})
}
}
It is clear that we've got convenient (for people with C#
, Python
background) library for text formatting. But we have another advantage - performance, sf
makes formatting **FASTER than fmt
**.
2. Perforamnce Benefits
There is one more important thing that could distinguish a sf
library: it has performance advances, both in formatting cases with argument format specifications and without them. But FormatComplex
is twice faster than fmt
, see picture below with the results:
3. Conclusion
Today we could say that there is one more text formatting utility/lib that has all fmt
features, and this library processes text faster, which in some cases could be important. Please give us a star on GitHub and subscribe.
Top comments (2)
I've tried it:
and the result on my machine (mac M3):
Normal seems faster and less allocations
@marcello_h, Repo contains benchmarks, my screenshots were obtained on
i7
CPU by running on a single core as follows (also running on another machine oni5
):go test -bench=Format -benchmem -cpu 1
go test -bench=Fmt -benchmem -cpu 1
I've runned with large statistic
~100 times
, and i could say that these vales ratio persists, andsf
is faster thanfmt