User Input & Output

Beginner Python
input()print()format()f-stringssys.stdout

Objective

Read user input and produce formatted output using print() and f-strings.

Tools & Technologies

  • input()
  • print()
  • format()
  • f-strings
  • sys.stdout

Key Commands

name = input('Name: ')
print(f'Hello, {name}!')
print('{:.2f}'.format(3.14159))
print('value:', x, sep='\t', end='\n')

Architecture Overview

flowchart LR USER[User types] -->|keyboard| INPUT[input() function] INPUT -->|returns string| VAR[Variable] VAR -->|process| PROC[Your code] PROC -->|result| PRINT[print() function] PRINT -->|stdout| SCREEN[Terminal output] style INPUT fill:#1a1a2e,stroke:#00d4ff,color:#e0e0e0 style PRINT fill:#1a1a2e,stroke:#00ff88,color:#e0e0e0

Step-by-Step Process

01
Input and Type Conversion

input() always returns a string — convert as needed.

name = input('Enter your name: ')  # string
age = int(input('Enter age: '))    # convert to int
temp = float(input('Temperature: '))

# Safe conversion with error handling
try:
    age = int(input('Age: '))
except ValueError:
    print('Please enter a number')
02
Formatted Output

Control how values are displayed.

# f-strings (most readable)
pi = 3.14159
print(f'Pi is approximately {pi:.2f}')
print(f'{'Left':<10} | {'Right':>10}')

# format() method
print('{} + {} = {}'.format(1, 2, 3))
print('{0:.2f} {1}'.format(3.14159, 'radians'))

# print parameters
print('a', 'b', 'c', sep='-')      # a-b-c
print('Loading...', end='')          # no newline
print(' Done!')

Challenges & Solutions

  • input() returns a string even when user types a number — convert before arithmetic
  • print() adds newline by default — use end='' to suppress

Key Takeaways

  • f-strings are 30-40% faster than % formatting in Python 3.6+
  • input() with no prompt is confusing — always provide a descriptive prompt string