input()

Read one line from stdin. Always str — cast if you need a number. Not for interactive apps.

Built-in functionPython 1.0+
Common call
name = input("Your name: ")
Returns
str — always
Replaces
the Python 2 `raw_input()` (Python 2 `input` evaluated the expression — a security hazard, now removed)
Watch out
always returns str; cast with int()/float() to get a number; raises EOFError at end-of-input
input(promptprompt — Optional prompt written to stdout without a trailing newline before reading. Empty string (default) skips the prompt.type: str · default: ""='')
→ str

Parameters

NameTypeRequiredDescription
promptstrno ("")Optional prompt written to stdout without a trailing newline before reading. Empty string (default) skips the prompt.

Return value

str — The user's input as a string. Reads until newline; the trailing newline is stripped. ALWAYS returns str — even if the user types a number. Cast with int() / float() if you need a number.

Common patterns

Get a string with a prompt
The everyday use.
name = input("Your name: ")
Get a number by casting
input never returns a number — always cast.
age = int(input("Age: "))
Validate with try/except
Casting can raise ValueError — handle gracefully.
try:
    age = int(input("Age: "))
except ValueError:
    print("must be a number")
Case-insensitive yes/no check
Casefold before comparing to avoid case bugs.
if input("Continue? ").strip().casefold() in ("y", "yes"):
    ...
Prefer argparse for scripts
CLI args are more testable than interactive prompts.
# argparse for tools; input() is for interactive prototypes

Examples

1. Basic
input("Name: ")
Returns
"Alice" # whatever the user typed
2. Always str
x = input("Number: ") type(x)
Returns
<class 'str'> # even if they typed 42
3. Cast to int
age = int(input("Age: "))
Returns
42
4. Cast to float
pi = float(input("π: "))
Returns
3.14
5. Blank input
input("Anything: ")
Returns
"" # empty string
6. End of input
input() # at EOF
Returns
EOFError

Pitfalls

1. input() ALWAYS returns str
The single most common input() bug. Even if the user types a number, you get the string form. Arithmetic on the result raises TypeError until you cast.
String math
x = input("Age: ")
x + 1
TypeError: can only concatenate str (not "int") to str
Cast to int
x = int(input("Age: "))
x + 1
43
2. The int() cast raises ValueError on non-numeric input
A user typing &quot;forty-two&quot; instead of &quot;42&quot; will crash your program if int() is unguarded. Wrap in try/except or validate first.
Uncaught error
int(input("Age: "))   # user types &quot;abc&quot;
ValueError: invalid literal for int() with base 10: 'abc'
Guarded cast
try:
    age = int(input("Age: "))
except ValueError:
    ...
handled
3. EOFError at end of input
When stdin runs out (piped input finished, Ctrl+D pressed), input() raises EOFError. In loops that read until quit, catch it or check for a specific sentinel.
Uncaught EOF
while True:
    line = input()
EOFError after stdin closes
Try/except
try:
    while True:
        line = input()
except EOFError:
    ...
clean exit
4. Python 2 input() vs raw_input()
Python 2 had TWO functions: input() (which called eval() — dangerous!) and raw_input() (which returned a string). Python 3 renamed raw_input to input and removed the eval-based version. If porting old Python 2 code, watch for input() calls that assumed evaluation.
Assumed eval
x = input("expr: ")   # Python 2: evaluated
silently different in Python 3
Explicit eval
x = eval(input("expr: "))   # only if safe!
clear intent

When to use

Use it
  • Interactive prompts in scripts and prototypes
  • REPL-like tools where the user types responses
  • Quick one-off &quot;ask the user&quot; questions
  • Learning material — input is the canonical &quot;get user data&quot; teaching tool
Reach for something else
  • Command-line arguments → argparse
  • GUI applications → the GUI framework&apos;s dialogs
  • Web apps → the HTTP request
  • Batch processing → read from a file or stdin non-interactively

Notes

Complexity
O(n) in the length of the line
Return
A string — always
CPython impl
Python/bltinmodule.c :: builtin_input — reads from stdin, strips trailing newline
Memory
Allocates one string
Thread-safe
Depends on the underlying stdin; not usually a concern in typical scripts

FAQ

Because input() returns a string. `"42" + 1` is a type error. Cast with `int(input(...))` or `float(input(...))` if you need a number.

History

1.0
input() and raw_input() both present in Python 1.0.
3.0
raw_input renamed to input; the eval-based input removed for security.