Update new_pattern.py

Author: lighting9999

new_pattern.py

@@ -1,28 +1,65 @@
-# pattern
-# @@@@@@@@    $
-# @@@@@@@    $$
-# @@@@@@    $$$
-# @@@@@    $$$$
-# @@@@    $$$$$
-# @@@    $$$$$$
-# @@    $$$$$$$
-# @    $$$$$$$$
+def main():
+    """Main function that gets user input and calls the pattern generation function."""
+    try:
+        lines = int(input("Enter number of lines: "))
+        if lines < 0:
+            raise ValueError("Number of lines must be non-negative")
+        result = pattern(lines)
+        print(result)
+    except ValueError as e:
+        if "invalid literal" in str(e):
+            print(f"Error: Please enter a valid integer number. {e}")
+        else:
+            print(f"Error: {e}")
+    except Exception as e:
+        print(f"An unexpected error occurred: {e}")
 
 
-def main():
-    lines = int(input("Enter no.of lines: "))
-    pattern(lines)
+def pattern(lines: int) -> str:
+    """
+    Generate a pattern of '@' and '$' characters.
+
+    Args:
+        lines: Number of lines to generate in the pattern
+
+    Returns:
+        A multiline string containing the specified pattern
+
+    Raises:
+        ValueError: If lines is negative
+
+    Examples:
+    >>> print(pattern(3))
+    @@@    $
+    @@    $$
+    @    $$$
+
+    >>> print(pattern(1))
+    @    $
 
+    >>> print(pattern(0))
+    <BLANKLINE>
 
-def pattern(lines):
-    t = 1
+    >>> pattern(-5)
+    Traceback (most recent call last):
+    ...
+    ValueError: Number of lines must be non-negative
+    """
+    if lines < 0:
+        raise ValueError("Number of lines must be non-negative")
+    if lines == 0:
+        return ""
+    
+    pattern_lines = []
     for i in range(lines, 0, -1):
-        nxt_pattern = "$" * t
-        pattern = "@" * (i)
-        final_pattern = pattern + "    " + nxt_pattern
-        print(final_pattern)
-        t = t + 1
+        at_pattern = "@" * i
+        dollar_pattern = "$" * (lines - i + 1)
+        pattern_lines.append(f"{at_pattern}    {dollar_pattern}")
+    
+    return "\n".join(pattern_lines)
 
 
 if __name__ == "__main__":
+    import doctest
+    doctest.testmod(verbose=True)
     main()