Indentation

Python uses indentation to indicate a block of code.

Leading whitespace (spaces and tabs) at the beginning of a statement is called indentation. 

• In Python, the same level of indentation associates statements into a single block of code. 
• The interpreter checks indentation levels very strictly and throws up syntax errors if indentation is not correct. 
• It is a common practice to use a single tab for each level of indentation.
• Python uses indentation for block as well as for nested block structures.