Python Crash Course: 챕터 4

Python Crash Course, 3rd Edition

 

• Using a Loop 
•  
• Starts with for and indentation is followed with a tab for PEP 8. Don't forget the colon.

magicians = ['alice', 'david', 'carolina']
for magician in magicians:
	print(f'They are all unqualified {magician}')

They are all unqualified alice
They are all unqualified david
They are all unqualified carolina

 

• Making numerical lists
• range() function generates a series of numbers

for value in range(1, 5):
 print(value)

1
2
3
4

Notice how the output never contains the end value, which would have been 5 in this case.

You can make a list of numbers using range() function and list() function.

numbers = list(range(1, 6))
print(numbers)

[1, 2, 3, 4, 5]

You can skip numbers in a given range by adding third arguement in range() function

numbers = list(range(2, 11, 2))
print(numbers)

[2, 4, 6, 8, 10]

 

• Simple Statistics with a list of numbers
• min() function - finds the smallest number
• max() function - finds the largest number
• sum() function - total sum of all numbers

 

• List Comprehension using Loop
• To use this syntax,
• 1. Begin with a descriptive name for the list
• 2. Define the expression for the values
• 3. Write a loop to generate the numbers you want to feed into the expression
  *The colon is not needed for the loop in List Comprehension

squares = [value**2 for value in range(1, 11)]
print(squares)

[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

•  

 

• Slicing a list

players = ['charles', 'martina', 'michael', 'florence', 'eli']
print(players[1:4])

• [1:4] can be interpreted as 'slice at index 1 and end it at index 4'
• Because Python stops one item before the second index 
•  
• you would get  1,2,3

players = ['charles', 'martina', 'michael', 'florence', 'eli']
print(players[-3:3])

[-3:3] can be interpreted as 'slice at negative index 3 and end it at index 3'

you would get 2

 

You can also add 'step' in slice to skip values in the list.

[:] is used to copy a list, enabling variables to have separate lists but values identical to each other.

 

• Tuples
• Tuples are immutable unlike lists.
• Closed by ( ) brackets not  [ ] square brackets

 

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