Reference · Crypto

crypto.sha256

crypto.sha256(str) -> str

What it does

The SHA-256 hash of the text, as 64 lower-case hex characters. The text is hashed as its UTF-8 bytes. The same text gives the same hash on every machine and every run, so it is for fingerprints, content addresses and checksums; for passwords use crypto.hash_password, which is salted and slow on purpose.

Examples

print(crypto.sha256("hello"))print(crypto.sha256("The quick brown fox jumps over the lazy dog"))

2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824d7a8fbb307d7809469ca9abcb0082e4f8d5651e46d3cdb762d02d0bf37c9e592

Edge cases

• The empty string has a hash too, the well-known e3b0c442....
• The result is always 64 characters, whatever the text's length.
• Letters outside ASCII hash as their UTF-8 bytes: "héllo" and "hello" differ.
• A value that is not text is hashed through its JSON: crypto.sha256(json.stringify(v)).

print(crypto.sha256(""))print(len(crypto.sha256("x")), len(crypto.sha256(repeat("x", 100000))))print(crypto.sha256("héllo") == crypto.sha256("hello"))print(crypto.sha256(json.stringify({ id: 7, tags: ["a"] })))

e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b85564 64false55f8a22c6c474bbfffb93b5637ac1035665decc79b0f12f9a1b0f2969119346d

Errors

An argument that is not a string is a runtime error, not an error value: null and numbers included. Convert with str or json.stringify first.

print(crypto.sha256(42))

line 1: `crypto.sha256` expects a str as argument 1, got int

print(crypto.sha256(null))

line 1: `crypto.sha256` expects a str as argument 1, got null

Chaining

The text is the only argument, so it reads well at the end of a pipeline, and the hex string can be cut with slice for a short id.

print("hello" | crypto.sha256)print("hello" | crypto.sha256 | slice(0, 12))print(["a", "b"] | map(crypto.sha256) | map((h) => slice(h, 0, 8)))

2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b98242cf24dba5fb0["ca978112", "3e23e816"]

See also

crypto.hmac, crypto.hash_password, crypto.equal, json.stringify, slice

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