------
## 最终结论
```python
def check_String(s):
    has_letter = False
    has_number = False
    for char in s:
        if char.isalpha():
            has_letter = True
        if char.isdigit():
            has_number = True
    if has_letter and has_number:
        return True
    else:
        return False

# Test cases
assert check_String('thishasboth29') == True
assert check_String('python') == False
assert check_String('string') == False
```