Converting in Both Directions

The full round trip you will use constantly:

text to number, do the arithmetic, number back to text for display.

Number to text

PYTHON

total = 51
message = "Total: " + str(total)
nice = f"Total: {total}"

JAVASCRIPT

const total = 51;
const message = "Total: " + String(total);
const nice = `Total: ${total}`;

Compare → Python needs str() to join a number onto a string with +. JavaScript converts automatically, which is convenient and occasionally surprising. Template strings avoid the whole question in both languages.

EXAMPLE

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YOUR TURN

Your turn → This is the real shape of processing a form submission. Change the quantity and rerun.

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Syntax has to be exact. Every quote, bracket and parenthesis needs its partner, and in Python the spaces at the start of a line count. One slip and the program won't run; the message will say where.

✦ When conversion fails

int("hello") raises a ValueError in Python and stops the program. Number("hello") in JavaScript quietly returns NaN, which stands for Not a Number, and then silently poisons every calculation it touches. Python shouts, JavaScript whispers. Both need checking.

EXAMPLE

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YOUR TURN

Your turn → Change "hello" to a real number written as text, like "7", so every line runs in both languages.

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Syntax has to be exact. Every quote, bracket and parenthesis needs its partner, and in Python the spaces at the start of a line count. One slip and the program won't run; the message will say where.

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