Does Go Convert Bytes to Runes When Accessing String Elements Individually?

Conversion During String Element Access in Go

In Go, accessing elements of a string returns bytes (uint8), despite their representation as runes (int32). However, when using for ... range on a string, you iterate over runes, not bytes. This raises the question:

Does Go perform conversion when accessing string elements individually (str[i])?

No, accessing str[i] does not require conversion. Strings are effectively read-only byte slices and indexing them directly accesses the underlying bytes.

Performance Considerations

Given that range iterations access runes and not bytes, let's compare the performance of two code snippets:

Option A: Direct string iteration

str := "large text"
for i := range str {
    // use str[i]
}

Option B: Conversion to byte slice

str := "large text"
str2 := []byte(str)
for _, s := range str2 {
    // use s
}

In reality, neither option involves copying or conversion. The second option is just a more verbose way of iterating over the same underlying byte slice. Therefore, there is no performance difference between the two.

Preferred Method

Given that there is no performance difference, the preferred method depends on the specific requirement:

• If you need to iterate over the bytes, use option B for clarity.
• If you need to iterate over the runes, use option A directly.

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