# Basic data type

## 1, Number (number)

### 1. Classification

• integer
• Floating point
• Boolean
• complex

### 2. Integer

• explain

python can handle integers of any size, including complex numbers

• General definition

```# General definition
num1 = 10
# ID (variable name): you can view the memory address of the variable
# Hex (decimal number): converts a decimal number to a hexadecimal number (beginning with 0x, not part of the data content)
print(id(num1), hex(id(num1)))
# Type (variable name): you can view the type of variable, int represents integer number
print(type(num1))```
• Continuous definition

```# Continuous definition
num2 = num3 = num4 = 5```
• Interaction definition

```# Interaction definition
num5, num6 = 1, 2```

```# Address problem (small integer object [- 5 ~ 256])
# If multiple variables are equal to small integer objects, the addresses of these variables are the same, because small integers are often used, which can save space and improve efficiency
num7 = 1
num8 = 1
num9 = 501
num10 = 501
print(id(num9), id(num10)) #The address is different. It needs to be executed under Linux```

### 3. Floating point

• explain

It consists of integral part and decimal part

• be careful

Operation may have rounding error

• Example

```num1 = 0.123434645
num2 = 0.2
print(num1 + num2)
print(type(num1), hex(id(num1)))
print(num1)```

### 4. Boolean value

Description: a boolean variable has only two values: True and False

Function: as a true or false judgment

```a = True
b = False
print(a, b)```

### 5. print supplement

```height = 173.555
print("lucky is a good man!His height is %f"%(height))
print("lucky is a good man!His height is %.2f"%(height))
age = 18
print("lucky is a nice man!He is *%d* years old"%(age))
print("lucky is a nice man!He is *%4d* years old"%(age))
print("lucky is a nice man!He is *%-4d* years old"%(age))```

### 6. Mathematical function

Description: operation of operands

• abs

```# Find absolute value
num1 = 5
num2 = abs(num1)
print("num2 = %s"%(num2))```
• max

• ```# Find the maximum of many numbers
num3 = max(2,3,5,6,1,5,77,54,2)
print("num3 = %s"%(num3))```
• min

```# Finding the minimum value of many numbers
print(min(2,3,5,6,1,5,77,54,2))```
• pow

```# Find the Y power of X pow(x, y)
print(pow(2,3))```
• round

```# rounding
# round(x[, n])  [round(x)   round(x, n)]
# Round x, n is the number of decimal places
print(round(3.1415926))
print(round(3.1415926, 4))```
• math.ceil

```# Import mathematics module
import math```
```# Round up
print(math.ceil(10.2))```
• math.floor

```# Round down
print(math.floor(10.9))```
• math.modf

```# Get the decimal and integer parts of floating-point numbers
# The result is a tuple. The first element of the tuple is the decimal part, and the second element is the integer part
print(math.modf(10.3))```
• math.sqrt

```# Square root
print(math.sqrt(10))```

### 7. Random function

Import random module

```# Import random module
import random```
• random.choice

```# choice(seq)
# Get an element at random from a sequence (set)
print(random.choice([1,2,4,3,5,6,7,8,9,0]))```
• random.randrange

```# randrange([start,]stop[,step])
# randrange(start,stop,step)
# randrange(start,stop)
# randrange(stop)
# Start: Specifies the start value of the range, included in the range, starting from 0 by default
# stop: Specifies the end value of the range, not included in the range
# Step: specify step value, default is 1
print(random.randrange(1, 10, 2))
print(random.randrange(1, 10))```
• random.random

```# random()
# Randomly generate a real number with a range of [0,1], and the result is a floating-point number
print(random.random())```
• random.uniform

```# uniform(x, y)
# Random Shencheng a real number, range in [x, y], get a floating point number
print(random.uniform(3, 7))```
• random.randint

```# randint(start, stop)
# Get an integer in the specified range [start, stop]
print(random.randint(1, 4))```

## 2, Character type

### 1. What is a string?

A string is any text enclosed in single or double quotation marks

```str1 = 'lucky is a good man'
str2 = "lucky is a nice man"```

be careful:

1. Quotation mark itself is a form of expression and does not belong to the content of string
2. If the string itself is enclosed with single quotation marks, the outer side is enclosed with double quotation marks ("he's a good man")

### 2. Multiline character

Any text with '' or ''

```str3 = '''
good
nice
cool
handsome'''

str4 = """
good
nice
cool
handsome"""```

Tags: Python Linux

Posted on Fri, 15 May 2020 11:55:53 -0400 by 758