Contents

• 2. Python Basics
  • 2.1 Comments
  • 2.2 Indentation and code blocks
  • 2.3 Input and output

2.1 Comments

• Single-line comment: A statement beginning with # is a comment.

# helloworld
print('hello world')

hello world

• Comment block: A block enclosed in ''' (three single quotes) or """ (three double quotes) acts as a comment.

'''
Function name: helloworld()
This function prints 'hello world'
'''
def helloworld():
    print('hello world')

helloworld()

hello world

2.2 Indentation and code blocks

• Indentation plays a very important role in Python, so use it carefully.

• Incorrect indentation causes an error. Indentation Error

• Indentation is determined by the number of spaces or tabs; using tabs is recommended for readability and consistency.

• Role 1: Indicates the scope of a loop or control statement.

print('start')
for i in range(10):
    if i>5:
        print('i = %d > 5' % i)
        # The if block ends here.
    elif i<5:
        print('i = %d < 5' % i)
    else:
        print('i = %d = 5' % i)
    # The for block ends here.
print('end')

start
i = 0 < 5
i = 1 < 5
i = 2 < 5
i = 3 < 5
i = 4 < 5
i = 5 = 5
i = 6 > 5
i = 7 > 5
i = 8 > 5
i = 9 > 5
end

• Role 2: Indicates the scope of a function or class definition.

def function1():
    print('  function start')
    print('  function end')
# The function body ends here.

print('script start')
function1()
print('script end')

script start
  function start
  function end
script end

2.3 Input and output

• Input input()
  • This function accepts keyboard input through the screen and stores it in a variable.

a = input()
print(a)

10
10

• Output print()
  • This function displays the desired content on the screen.
  • Write the expression to display between ' '.
  • For content that varies with a variable, use %d (integer), %f (real number), or %s (string), according to its type.
    • %.1f (display a real number to one decimal place)
  • Put % to the right of ' ', then list the variables to substitute into the expression in order inside ( ).

i = 4
j = 4.5
k = 'abc'
print('i=%d j=%.1f k=%s' % (i,j,k))

i=4 j=4.5 k=abc