This document discusses Python statements, code blocks, and indentation. It notes that statements in Python are typically written on individual lines, but can span multiple lines using line continuation characters or parentheses. Code blocks, like if/else statements and functions, are defined by indentation rather than brackets - any indented code will be executed as part of the code block. Indentation is significant in Python and code blocks must be indented consistently using spaces.

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Statements, Code Blocks and Indentation
Pavan Verma
Python Programming Essentials
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@YinYangPavan

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Python statements
 A statement is a one Python instruction
 Most of the time, there is exactly one Python
statement per line
>>> x = 4 + 6
>>> y = x**2
>>> print y
100
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Multiple statements on one line
 It’s possible to have multiple statements,
separated by semi-colon, on a single line
 Doing so is NOT recommended as it reduces
code readability
>>> x = 4 + 6; y = x**2; print y
100
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Statements can span multiple lines
 There are two ways to make a statement span
multiple lines
 Use it if it improves code readability by
breaking a very long statement
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>>> x = 4 +
6
>>> x
10
>>> x = (4
+
6)
>>> x
10

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Code blocks
 A code block is a set of statements that will be
executed together, one after the other
 if statements, for loops, while loops, functions, are all
code blocks
if x > 10:
is_greater = True
print "Greater than 10"
else:
is_greater = False
print "Not greater than 10"
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Code blocks and Indentation
 Code blocks have no explicit begin or end. There
are no explicit braces, brackets, or keywords.
 Code blocks are defined by their indentation
• Indenting starts a block and unindenting ends it
• The only delimiter is a colon (:) and the indentation
of the code itself
 This means that whitespace is significant, and
must be consistent
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Sample code blocks
def fib(n):
print 'n = ', n
if n > 1:
return n * fib(n-1)
else:
print 'end'
return 1
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Sample code blocks (2)
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def fib(n):
print 'n = ', n
if n > 1:
return n * fib(n-1)
else:
print 'end'
return 1

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Sample code blocks (3)
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def fib(n):
print 'n = ', n
if n > 1:
return n * fib(n-1)
else:
print 'end'
return 1

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Sample code blocks (4)
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def fib(n):
print 'n = ', n
if n > 1:
return n * fib(n-1)
else:
print 'end'
return 1

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Indentation Tips
 Use 4 spaces per indentation level
 Spaces are the preferred indentation method
 Use spaces for indentation; not tabs
• 1 tab == 1 indent level
 Python 3 explicitly disallows mixing the use of
tabs and spaces for indentation
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Summary
 Statements
 Relationship between Python statements
and lines
 Code blocks
 Relationship between code blocks and
indentation in Python
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