数学建模

 

编程知识点

编程基础-Python-Why Python

 

Wang Haihua

🚅 🚋😜 🚑 🚔

What is Python?

• Python is an interpreted, general-purpose programming language (This means the machine doesn't directly run your code. our code is line by line converted into low level machine language)
• It supports object-oriented concepts (classes, objects etc.)
• Dynamically typed - so the type of a variable is decided at runtime, which means you don't have to specify it in yhe code.

Code and Comments

print("Hello World!")

Hello World!

Python runs the code line by line:

print("Hello1")
print("Hello2")
print("Hello3")
print("Welcome to Our Python course")

Hello1
Hello2
Hello3
Welcome to Our Python course

If you make mistakes, python will complain:

print("Hello')

  File "<ipython-input-3-21f0c5b97628>", line 1
    print("Hello')
                  ^
SyntaxError: EOL while scanning string literal

print "Hello World"

  File "<ipython-input-4-2e860ebf713e>", line 1
    print "Hello World"
          ^
SyntaxError: Missing parentheses in call to 'print'. Did you mean print("Hello World")?

print(Hello)

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-5-85bf5114fa6b> in <module>
----> 1 print(Hello)

NameError: name 'Hello' is not defined

Checking the Version

!python --version

Python 3.8.5

Comment

#this is where I print "Hello World" 

#taking some notes
#take a note

Data Types

• Text type: str (string)
• Numeric types: int (integer), float (and complex)
• Sequence types: list, tuple, range
• Mapping type: dict (dictionary)
• Boolean type: boolean
• Set type: set

Variables

We can use variables to store values

For example:

• variable = value

• n = 5

n = 1 
print(n)

1

p = n
print(p)

1

#swapping
data1 = 7 
data2 = 12
data3 = 23
data4 = 33

data1, data2, data3 , data4 = data2 , data1, data4, data3
print(data1, data2, data3, data4)

12 7 33 23

print("data1:", data1, "data:", data2)

data1: 12 data: 7

String (str)

Think of this as a sequence of characters

M	y		n	a	m	e		i	s		G	a	b	b	y
0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15

#String
hello = "World"

print(hello) #print variable
print("World") #print value
print(n)

World
World
1

type('x')

str

#type() 
type(hello)

str

print(type(hello)) #print data type

<class 'str'>

Integer (int)

#Integer
int_value = 5
int_value

5

print(type(int_value))

<class 'int'>

Float

t = 3.19
print(type(t))

<class 'float'>

Boolean (bool)

#Boolean
t, f = True, False
print(type(t))
print(t)
print(f)

<class 'bool'>
True
False

String Operations

len()

Gets the length of a string

len("Python")

6

len("Welcome to the Turkish AI Hub")

29

hello

'World'

print(len(hello)) #print data length 

5

p

1

len(5)

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-26-91fed648bb37> in <module>
----> 1 len(5)

TypeError: object of type 'int' has no len()

len(15.6)

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-27-79577706af1a> in <module>
----> 1 len(15.6)

TypeError: object of type 'float' has no len()

data22 = "Data Science"
len(data22) 

12

len("Data Science")

12

Concatenating Strings

name = "Omer"
print(name)
name = name + " Cengiz"
print(name)

Omer
Omer Cengiz

String Formatting

#F-string
name = "Turkey"
print(f'hello {name}') 

hello Turkey

name2 = "Aslı"
print("Hello {}".format(name2))

Hello Aslı

data12 = 5
data13 = 90
print("My value:{} and Your value:{}".format(data12, data13))

My value:5 and Your value:90

print(f'My value: {data12} and your value: {data13}')

My value: 5 and your value: 90

print("My value:", str(data12), "Your Value:", str(data13))

My value: 5 Your Value: 90

Arithmetic Operators

Operator	Name
+	Addition
-	Subtraction
*	Multiplication
/	Division
//	Floor division
**	Exponentiaion
%	Modulus

These operators can be used like the following:

On Numerical Values:

35+67

102

#exponential numbers
5**2

25

5**3

125

x = 10

print(x+2)

12

y = 13
print(y/2)
print(y//2)
print(y % 2)

6.5
6
1

x = "35" + 67 

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-41-e19ba8062dfb> in <module>
----> 1 x = "35" + 67

TypeError: can only concatenate str (not "int") to str

On Strings:

my_string = "hello" + "world"
print(my_string)

helloworld

my_string = "35"*3
print(my_string)

353535

my_string = "hello"*4
print(my_string)

hellohellohellohello

(Additional) Assignment Operators (+= , *= etc)

z = 5
z += 1 # this statement equals to z= z+1 , meaning while the previous value of z is 5, the new z value becomes 6. 
z

6

z += 2 #z = z + 2
z

8

z *= 2      # z = z * 2
z

16

my_string = "hey"
print(my_string)
my_string += " there"
print(my_string)
my_string *= 2
print(my_string)

hey
hey there
hey therehey there

Docstrings (documentation strings)

"""
These quotes are used for docstrings. They are often confused with comments. But python will treat this as a regular string
"""

'\nThese quotes are used for docstrings. They are often confused with comments. But python will treat this as a regular string\n'

References

• https://github.com/SudePehlivanoglu/python-education-v2