all Python 3sysfunction

sys.displayhook()

debugging and tracing

The function the interactive interpreter (REPL) uses to show the result of an entered expression and to store it in the _ variable.

Syntax

sys.displayhook(value)

It is never called in a script: a bare expression 2 + 2 in a file prints nothing, unlike the REPL — a common cause of 'empty output' in a submitted solution. For None it shows nothing, which is why the console hides the result of print(). Replacing sys.displayhook changes how the REPL shows answers, for example with pprint; the original is sys.__displayhook__.

Examples

import builtins, sys
sys.displayhook(42)  # → 42
print(builtins._)  # → 42
sys.displayhook(None)
print(builtins._)  # → 42

See also

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