Summary
Safely parse and validate integers from user input strings.
Problem statement
Many programs accept text input and need to interpret integers safely. Implement a function validate_integer(s, min_value=None, max_value=None) that tries to convert the input s to an int. If conversion succeeds and the value is within the optional min_value and max_value (inclusive) constraints, return the int. For any invalid input (non-integer strings, floats like '3.0', values out of range), return None. The function should tolerate leading/trailing whitespace and plus/minus signs.
Task
Write a function that converts input to an integer only when valid and optionally enforces min/max bounds.
Examples
Valid integer string
Input
validate_integer('42')
Output
42
Explanation
The string '42' converts to integer 42 and no bounds are set.
Whitespace and sign
Input
validate_integer(' -7 ')
Output
-7
Explanation
Leading/trailing whitespace and a minus sign are handled; returns -7.
Input format
A single call validate_integer(s, min_value=None, max_value=None) where s is typically a string.
Output format
Return an int when the input is a valid integer within bounds, otherwise return None.
Constraints
Do not accept strings that represent floats ('3.0') or scientific formats that aren't integer-valued. Use safe parsing and avoid raising exceptions to the caller.
Samples
Sample input 0
validate_integer('10', min_value=0, max_value=20)
Sample output 0
10
Explanation 0
10 is within the range 0..20 so returned as int.
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