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<!DOCTYPE html>
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  <meta name="description"
        content="Chapter 4 of Python Zero to Hero: learn console input/output with print(), input(), and string formatting." />
  <meta name="keywords"
        content="Python, console I/O, print, input, f-strings, format, string interpolation" />
  <meta name="author" content="Luca Bocaletto" />
  <title>Chapter 4 – Console I/O | Python Zero to Hero</title>

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      <h1 class="display-6">Chapter 4: Console I/O</h1>
      <p class="text-muted">
        Master console input and output: <code>print()</code>, <code>input()</code>,
        and various string formatting techniques.
      </p>
      <a href="src/chapter4.py" download class="btn btn-outline-primary btn-sm btn-py">
        Download <code>chapter4.py</code>
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      <h2>Objectives</h2>
      <ul>
        <li>Use <code>print()</code> with <code>sep</code>, <code>end</code> and <code>flush</code>.</li>
        <li>Read user input via <code>input()</code> and convert types.</li>
        <li>Format strings with f-strings, <code>str.format()</code>, and <code>%</code> operator.</li>
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    <!-- 1. print() -->
    <section id="print" class="mb-5">
      <h2>1. The print() Function</h2>
      <p>Print values to console. Default <code>sep=' '</code>, <code>end='\n'</code>:</p>
      <pre><code class="python">print("Hello", "World")           # Hello World
print("No newline", end="")           # stays on same line
print(" → next")</code></pre>
      <p>Customize separator and flush:</p>
      <pre><code class="python">print(1, 2, 3, sep=" - ")          # 1 - 2 - 3
import sys
print("Immediate", flush=True)         # flushes buffer</code></pre>
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    <!-- 2. input() -->
    <section id="input" class="mb-5">
      <h2>2. The input() Function</h2>
      <p>Prompt the user and read a line (returns <code>str</code>):</p>
      <pre><code class="python">name = input("Enter your name: ")
age_str = input("Enter your age: ")
age = int(age_str)                    # convert to int
print(f"Name: {name}, Age: {age}")</code></pre>
      <p>Always handle conversion errors:</p>
      <pre><code class="python">try:
    num = int(input("Number: "))
except ValueError:
    print("Invalid number!")</code></pre>
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      <h2>3. String Formatting</h2>
      <h3>a) f-strings (Python 3.6+)</h3>
      <pre><code class="python">user = "Alice"
score = 95.5
print(f"{user} scored {score:.1f} points")</code></pre>
      <h3>b) str.format()</h3>
      <pre><code class="python">template = "{} has {} apples"
print(template.format("Bob", 3))</code></pre>
      <h3>c) % Operator</h3>
      <pre><code class="python">fmt = "Total: %d items, %0.2f$"
print(fmt % (7, 15.239))</code></pre>
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        <li>Write a script that asks for three numbers, prints their sum.</li>
        <li>Prompt for first/last name separately and greet with an f-string.</li>
        <li>Build a small menu: ask “1) Add  2) Subtract”, read choice, perform on two inputs.</li>
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