Bài trước: Python căn bản (5): Data Types
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6. Python Numbers
6.1 Numeric types in Python
There are three numeric types in Python: int, float and complex
Variables of numeric types are created when you assign a value to them.
To verify the type of any object in Python, use the type() function.
Example:
x = 1 # int
y = 2.8 # float
z = 1j # complex
print(type(x))
print(type(y))
print(type(z))
Int
Int, or integer, is a whole number, positive or negative,
without decimals, of unlimited length.
Example
x = 1
y = 35656222554887711
z = -3255522
print(type(x))
print(type(y))
print(type(z))
Float
Float, or "floating point number" is a number, positive or negative,
containing one or more decimals.
Example
x = 1.10
y = 1.0
z = -35.59
print(type(x))
print(type(y))
print(type(z))
Float can also be scientific numbers with an "e" to indicate the power of 10.
Example
x = 35e3
y = 12E4
z = -87.7e100
print(type(x))
print(type(y))
print(type(z))
Complex
Complex numbers are written with a "j" as the imaginary part.
Example
x = 3+5j
y = 5j
z = -5j
print(type(x))
print(type(y))
print(type(z))
6.2 Type Conversion
You can convert from one type to another with the int(), float(), and complex() methods.
Example
x = 1 # int
y = 2.8 # float
z = 1j # complex
#convert from int to float:
a = float(x)
#convert from float to int:
b = int(y)
#convert from int to complex:
c = complex(x)
print(a)
print(b)
print(c)
print(type(a))
print(type(b))
print(type(c))
Note: You cannot convert complex numbers into another number type.
6.3 Random Number
Python does not have a random() function to make a random number, but Python has a built-in module called random that can be used to make random numbers.
Example
Import the random module, and display a random number between 1 and 9:
import random
print(random.randrange(1,10))
6.4 Python Casting
Specify a Variable Type
There may be times when you want to specify a type on a variable. This can be done with casting. Python is an object-oriented language, and as such it uses classes to define data types, including its primitive types.
Casting in python is therefore done using constructor functions:
int() - constructs an integer number from an integer literal, a float literal (by removing all decimals), or a string literal (providing the string represents a whole number)
float() - constructs a float number from an integer literal, a float literal or a string literal (providing the string represents a float or an integer)
str() - constructs a string from a wide variety of data types, including strings, integer literals and float literals
Example
Integers:
x = int(1) # x will be 1
y = int(2.8) # y will be 2
z = int("3") # z will be 3
print(x)
print(y)
print(z)
Floats:
x = float(1) # x will be 1.0
y = float(2.8) # y will be 2.8
z = float("3") # z will be 3.0
w = float("4.2") # w will be 4.2
print(x)
print(y)
print(z)
print(w)
Strings:
x = str("s1") # x will be 's1'
y = str(2) # y will be '2'
z = str(3.0) # z will be '3.0'
print(x)
print(y)
print(z)
6.5 Exercise
1. Which is NOT a legal numeric data type in Python?
A. int
B. long
C. float
D. complex
2. What will be the result of the following code:
print(int(35.88))
A. 35
B. 35.00
C. 36
D. 35.88
3. What will be the result of the following code:
print(float(35))
A. 35
B. 35.0
C. ‘35’
D. 0.35
4. Write a Python program that allows user input two numbers, then calculate the product and sum of two numbers.
Input:
Number 1:3
Number 2:4
Expected output:
Product: 12
Sum: 7
5. Write a Python program that allows user input the length and width of the rectangle, then calculate the perimeter and area of the rectangle.
Input:
Length:2.5
Width 3.0
Expected output:
Perimeter: 11.0
Area: 7.5
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Cập nhật: 27/9/2024
Bài sau: Python căn bản (7): Python Strings
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