To determine the number of numerical digits in a string, you can follow these steps:

**Understand the Problem**: You need to count how many characters in a string are digits. Digits are characters like`0`

,`1`

,`2`

, …,`9`

.**Break Down the Problem**:**Input**: A string of characters (e.g.,`"Hello 123 World 45"`

).**Output**: The count of digits in that string (e.g.,`5`

for the example above).

**Steps to Solve**:**Step 1**: Traverse through each character in the string.**Step 2**: Check if the character is a digit.**Step 3**: Count each digit you find.**Step 4**: Return the total count.

**Example**:- Input String:
`"My phone number is 123-4567."`

- The digits in the string are:
`1`

,`2`

,`3`

,`4`

,`5`

,`6`

,`7`

- The total count of digits is
`7`

.

- Input String:
**Code Example in Python**:

Here’s a detailed Python code to achieve this:

```
def count_digits(s):
# Initialize a counter to keep track of digits
digit_count = 0
# Traverse each character in the string
for char in s:
# Check if the character is a digit
if char.isdigit():
# Increment the counter if it's a digit
digit_count += 1
# Return the total count of digits
return digit_count
# Example usage
input_string = "My phone number is 123-4567."
result = count_digits(input_string)
print("Number of digits in the string:", result)
```

### Detailed Explanation:

**Function Definition**:`def count_digits(s)`

: This defines a function`count_digits`

that takes one parameter,`s`

, which is the input string.

**Initialize Counter**:`digit_count = 0`

: Start with a counter set to`0`

to keep track of the number of digits.

**Loop Through Characters**:`for char in s`

: Loop through each character in the string`s`

.

**Check for Digits**:`if char.isdigit()`

: Use the`isdigit()`

method to check if the character is a digit. This method returns`True`

if the character is a digit and`False`

otherwise.

**Update Counter**:`digit_count += 1`

: If the character is a digit, increment the`digit_count`

by`1`

.

**Return the Count**:`return digit_count`

: After the loop, return the total count of digits.

**Example Usage**:`input_string = "My phone number is 123-4567."`

: This is the string we are testing.`result = count_digits(input_string)`

: Call the function and store the result.`print("Number of digits in the string:", result)`

: Print the result.

By following these steps and using the provided code, you can easily calculate the number of numerical digits in any given string.