Understanding inputNum() from PyInputPlus with Examples

byOnly Python -

Deep Dive into inputNum() with Examples and Outputs

This post explores inputNum() from PyInputPlus with basic-to-moderate examples, demonstrating how to validate numeric input, enforce ranges, handle timeouts/limits, and more.

Why Use inputNum()?

Instead of using input() plus manual conversion and try/except for numeric validation, inputNum() automatically ensures the user enters a valid number (int or float). It also supports parameters like min, max, greaterThan, lessThan, limit, timeout, and default to streamline your input-handling logic.


import pyinputplus as pyip

# Basic numeric input: automatically retries until a valid number is entered.
num = pyip.inputNum("Enter any number: ")
print(f"Received number: {num} (type: {type(num)})")

Sample Interaction & Output:


Enter any number: abc
'abc' is not a number.
Enter any number: 42
Received number: 42 (type: <class 'int'>)

Allow Only Integers or Floats Explicitly

By default, inputNum() accepts integers and floats. If you want strictly integers, use inputInt(); for strictly floats, use inputFloat(). But if you want to accept both, inputNum() is convenient:


import pyinputplus as pyip

value = pyip.inputNum("Enter integer or float: ")
print(f"Value: {value} (type: {type(value)})")
# If you need only integers:
int_value = pyip.inputInt("Enter integer only: ")
# If you need only floats:
float_value = pyip.inputFloat("Enter float only: ")

Sample Interaction & Output:


Enter integer or float: 3.14
Value: 3.14 (type: <class 'float'>)
Enter integer only: 5
Enter float only: five
'five' is not a number.
Enter float only: 2.718

Enforce a Range with min and max

Require the entered number to lie within a specified inclusive range. Useful for age checks, menu selections, etc.


import pyinputplus as pyip

# Example: age between 18 and 65 inclusive
age = pyip.inputNum("Enter your age (18–65): ", min=18, max=65)
print(f"Age accepted: {age}")

Sample Interaction & Output:


Enter your age (18–65): 17
Number must be at minimum 18.
Enter your age (18–65): seventy
'seventy' is not a number.
Enter your age (18–65): 30
Age accepted: 30

Use greaterThan and lessThan for Exclusive Bounds

If you need strict inequalities (exclusive), use greaterThan and/or lessThan:


import pyinputplus as pyip

# Strictly greater than 0 and strictly less than 1
frac = pyip.inputNum("Enter a fraction between 0 and 1 (exclusive): ", greaterThan=0, lessThan=1)
print(f"You entered: {frac}")

Sample Interaction & Output:


Enter a fraction between 0 and 1 (exclusive): 0
Number must be greater than 0.
Enter a fraction between 0 and 1 (exclusive): 1
Number must be less than 1.
Enter a fraction between 0 and 1 (exclusive): 0.5
You entered: 0.5

Custom Error Messages with errorMsg

You can override the default messages when validation fails:


import pyinputplus as pyip

# Custom message for out-of-range
num = pyip.inputNum(
    "Pick a number from 1 to 10: ",
    min=1, max=10,
    errorMsg="Please enter a valid number between 1 and 10!"
)
print(f"Chosen: {num}")

Sample Interaction & Output:


Pick a number from 1 to 10: 11
Please enter a valid number between 1 and 10!
Pick a number from 1 to 10: abc
'abc' is not a number.
Pick a number from 1 to 10: 7
Chosen: 7

Limit Attempts with limit and default

Allow only a certain number of invalid attempts; after exceeding, return a default value:


import pyinputplus as pyip

# Only 2 invalid attempts, then default of -1
num = pyip.inputNum(
    "Enter priority (1-5): ",
    min=1, max=5,
    limit=2, default=-1
)
print(f"Priority: {num}")

Sample Interaction & Output:


Enter priority (1-5): 0
Number must be at minimum 1.
Enter priority (1-5): 10
Number must be at maximum 5.
Priority: -1

Or if valid within attempts:


Enter priority (1-5): 3
Priority: 3

Timeout with timeout and default

Wait for input up to a specified number of seconds; if the user does not respond in time, return the default (or raise TimeoutException if no default provided):


import pyinputplus as pyip

# Wait up to 4 seconds; use -1 if timed out
try:
    num = pyip.inputNum(
        "Enter a number within 4 seconds: ",
        timeout=4, default=-1
    )
except pyip.TimeoutException:
    num = -1
    print("Timed out; default used.")
print(f"Result: {num}")

Sample Interaction & Output (timeout):


Enter a number within 4 seconds: 
(no input for 4 seconds)
Result: -1

Sample Interaction & Output (valid input):


Enter a number within 4 seconds: 12
Result: 12

Combine min/max, greaterThan/lessThan, limit, timeout, and default

Examples combining multiple parameters for robust input handling:


import pyinputplus as pyip

# Example: optional discount percentage: allow blank entry, otherwise between 0 and 100
discount = pyip.inputNum(
    "Enter discount % (0–100) or wait 3s for default: ",
    min=0, max=100,
    timeout=3, default=0
    )
print(f"Discount: {discount}%")

Sample Interaction & Output (timeout):


Enter discount % (0–100) or wait 3s for default: 

Discount: 0%

Sample Interaction & Output (valid entry):


Enter discount % (0–100) or wait 3s for default: 25
Discount: 25%

Happy coding!

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