Basic data type, java Basic Data Type

Basic data type, java Basic Data Type
1. Numbers

 

1 >>> 7 + 3 # Addition 2 10 3 >>> 7-3 # subtraction 4 4 4 5 >>> 7*3 # multiplication 6 21 7 >>> 7/3 # Division 8 2 9 >>> 5 ** 2 # Multiplication Side 10 2511 >>>> 7% 3 # evaluate the remainder 12 113 >>>> a = 7.0/2 # float divided by int, result: float14 >>> print a, type (a) 15 3.5 <type 'float'>

2. Strings

 1 >>>word=’Python’ 2 >>>word[0] 3 ‘P’ 4 >>>word[5] 5 ‘n’ 6 >>>word[-1] 7 ‘n’ 8 >>>word[-2] 9 ‘o’10 >>>word[-6]11 ‘P’12 13 >>>word[0:2]14 ‘Py’15 >>>word[2:5]16 ‘tho’17 >>>word[:2]18 ‘Py’19 >>>word[-2:]20 ‘on’21 >>>word[:2]+word[2:]22 ‘Python’23 >>>len(word)24 6

+ --- +

| P | y | t | h | o | n |

+ --- +

0 1 2 3 4 5 6

-6-5-4-3-2-1

 

The sequence number of the string "Python", sorted from left to right by 0-6, from right to left (-1)-(-6)

 

3. Lists

 

1 >>> squares = [, 25] 2 >>> squares 3, 25] 4 >>> squares [0] 5 1 6 >>> squares [-1] 7 25 8 >>> squares [-3:] 9 [9, 16, 25] 10 >>> squares [:] # returns a copy of squares, that is, the new list11 [, 25] 12 >>>> squares +, 100] 13 [81,100,] 14 15> cubes =, 125] 16 >>> 4 ** 3 #4 cubes are 6417 64 18 >>> cubes [3] = 6419 >>>> cubes20 [, 64, 125] 21 >>> cubes. append (216) 22 >>> cubes. append (7 ** 3) 23 >>> cubes24 [125,216,343,] 25 26 >>> letters = ['A', 'B', 'C ', 'D', 'E', 'F', 'G'] 27> letters28 ['A', 'B', 'C', 'D ', 'E', 'F', 'G'] 29 >>> letters [2: 5] = ['C', 'D ', 'E'] 30 >>> letters31 ['A', 'B', 'C', 'D', 'E', 'F ', 'G'] 32 >>> letters [2: 5] = [] 33 >>> letters34 ['A', 'B', 'F ', 'G'] 35 >>> letters [:] = [] 36 >>> letters37 [] 38 39 >>> letters = ['A', 'B ', 'C', 'D'] 40 >>> len (letters) 41 442 43 >>> a = ['A', 'B ', 'C'] 44 >>> n = [1, 2, 3] 45 >>> x = [a, n] 46 >>> x47 [['A ', 'B', 'C'], [1, 2, 3] 48 >>> x [0] 49 ['A', 'B ', 'C'] 50 >>> x [0] [1] 51 'B'

 

4. Summary

Variables do not need to be declared or deleted. They can be recycled directly.

Type (): query data type

Difference between String and List: String can only be read. It cannot be replaced by an equal sign (=) value assignment. List can be read. It can also be replaced by an equal sign (=) value assignment.