---
tags: Python
---
# Python studying memo
###### tags: `python`
## virtualenv
### create new virtual environment
```bash=
sudo apt-get install python3
sudo apt-get install python-pip
pip3 install --upgrade
pip3 install virtualenv
virtualenv -p python3 [virtual_environment_name]
# ex: virtualenv -p python3 tf_2012_tf1_py3
# After that, it will create a folder named tf_2012_tf1_py3, and it contains two folders: bin and lib
```
### run in a created virtual environment
```bash=
. ./[vitrual_environment_name]/bin/activate
```
### exit virtual environment
```bash=
deactivate
```
## 精通Python 讀後筆記 (未完成)
### Note
I only read a little, because I may not used all of these content
### book_url_example
```python=
import webbrowser
import requests
import json
from urllib.request import urlopen
print("Let us find an old website.")
site = input("Type a website URL: ")
era = input("Type a year, month and a day, like 20150613: ")
url = "http://archive.org/wayback/available?url=%s×tamp=%s" % (site, era)
response = urlopen(url)
contents = response.read()
text = contents.decode("utf-8")
data = json.loads(text)
try:
old_site = data["archived_snapshots"]["closest"]["url"]
print("Found this copy: ", old_site)
print("It should appear in your browser now")
webbrowser.open(old_site)
except:
print("Sorry, no luck finding", site)
```
```python=
print("Let us find an old website.")
site = input("Type a website URL: ")
era = input("Type a year, month and a day, like 20150613: ")
url = "http://archive.org/wayback/available?url=%s×tamp=%s" % (site, era)
response = requests.get(url)
data = response.json()
try:
old_site = data["archived_snapshots"]["closest"]["url"]
print("Found this copy: ", old_site)
print("It should appear in your browser now")
webbrowser.open(old_site)
except:
print("Sorry, no luck finding", site)
```
### variable
```python=
var_num = 123
type(var_num) # int
var_str = '456'
type(var_str) # str
print(var_num+int(var_str)) # output: 579 # (datatype: int)
print(str(var_num)+var_str) # output: 123456 # (datatype: str)
```
### print
```python=
var_name = input('Your Name : ')
print('Your Name : ' + var_name)
```
### if-else
```python=
var_money = input('Your Money : ')
if int(var_money) > 600:
print('badminton')
elif int(var_money) < 600 and int(var_money) > 300:
print('eat')
else:
print('go home and sleep')
```
### list
```python=
spells = [
"Riddikulus!",
"Wingardium Leviosa!",
"Avada Kedavra!",
"Expecto Patronum!",
"Nox",
"Lumos",
]
print(spells[2]) # output: Acada Kedavra!
print(spells) # output: ['Riddikulus!', 'Wingardium Leviosa!', 'Avada Kedavra!', 'Expecto Patronum!', 'Nox', 'Lumos']
spells.append("Sectumsempra") # added var to 'last' place of list
print('after list.append, ', spells) # output: after list.append, ['Riddikulus!', 'Wingardium Leviosa!', 'Avada Kedavra!', 'Expecto Patronum!', 'Nox', 'Lumos', 'Sectumsempra']
spells.insert(2,"Crucio") # added var to the place which you pointed to
print('after list.insert, ', spells) # output: ['Riddikulus!', 'Wingardium Leviosa!', 'Crucio', 'Avada Kedavra!', 'Expecto Patronum!', 'Nox', 'Lumos', 'Sectumsempra']
spells.pop() # if there is no parameter for list.pop method, it automaticly delected last value of the list
print('after list.pop, ', spells) # output: ['Riddikulus!', 'Wingardium Leviosa!', 'Crucio', 'Avada Kedavra!', 'Expecto Patronum!', 'Nox', 'Lumos']
del_num = 2
print('del_num : ', del_num)
spells.pop(del_num) # output: 'Crucio' # deleted list[2] value
print('after list', del_num,'.pop, ', spells) # output: ['Riddikulus!', 'Wingardium Leviosa!', 'Avada Kedavra!', 'Expecto Patronum!', 'Nox', 'Lumos']
spells.insert(0,"Avada Kedavra!") # input "Avada Kedavra" at list[0]
print('after list.insert, ', spells) # output: ['Avada Kedavra!', 'Riddikulus!', 'Wingardium Leviosa!', 'Avada Kedavra!', 'Expecto Patronum!', 'Nox', 'Lumos']
spells.remove("Avada Kedavra!") # delected all value "Avada Kedavra" in list
print('after list.remove, ', spells) # output: ['Riddikulus!', 'Wingardium Leviosa!', 'Avada Kedavra!', 'Expecto Patronum!', 'Nox', 'Lumos']
spells.clear() # clear the list
print(spells) # output: []
```
```python=
list_num = [
2,
5,
3,
8,
9,
22,
]
print(list_num[2]) # output: 3
print(list_num) # output: [2, 5, 3, 8, 9, 22]
list_num.append(15) # added var to last place of list
print('after list_num.append, ', list_num) # output: [2, 5, 3, 8, 9, 22, 15]
list_num.insert(2,16) # added var 16 to place 2 of list
print('after list_num.insert, ', list_num) # output: [2, 5, 16, 3, 8, 9, 22, 15]
print('max : ', max(list_num)) # output: max : 22
print('min : ', min(list_num)) # output: min : 2
print('sum : ', sum(list_num)) # output: sum : 80
print('list_num.length : ', len(list_num)) # output: list_num.length : 8
print('2nd to 4th place of list_num : ', list_num[1:4]) # output: 2nd to 4th place of list_num : [5, 16, 3]
```
### for_loop
```python=
for cnt in range(1, 10):
print(cnt)
"""
output:
1
2
3
4
5
6
7
8
9
"""
print("\n")
for cnt in range(2, 20, 2):
print(cnt)
"""
output:
2
4
6
8
10
12
14
16
18
"""
print("\n")
for cnt in range(20, 2, -2):
print(cnt)
"""
output:
20
18
16
14
12
10
8
6
4
"""
for countdown in 5, 4, 3, 2, 1, "hey!!!":
print(countdown)
"""result will be :
5
4
3
2
1
hey!!!"""
```
### dictionary
```python=
quotes = {
"Moe": "A wise guy, huhy?",
"Larry": "Ow!",
"Curly": "Nyuk nyuk!",
}
Name = "Larry"
print(Name, "says", quotes[Name]) # output: Larry says Ow!
```
### function
```python=
def hello_world():
print('hello world')
def print_variable(i):
print('input variable : ',i)
def plus(a,b):
c = (int(a) +int(b))
print(a, '+', b, '=', c)
hello_world()
print_variable('500')
plus_one = 3
plus_two = 5
plus(plus_one, plus_two) # output: 3 + 5 = 8
```
### object
```python=
class Animal():
def set_age(self, age):
self.age = age
def say_my_age(self):
print("My age is : ", self.age)
def howl(self):
print("HELLO PYTHON")
class Cat(Animal):
def set_name(self, name):
self.name = name
def say_my_name(self):
print("My name is : ", self.name)
cat_a = Cat()
cat_a.set_age('26')
cat_a.set_name('Tom')
cat_a.howl() # output: HELLO PYTHON
cat_a.say_my_age() # output: My age is : 26
cat_a.say_my_name() # My name is : Tom
```
```python=
class Animal:
def __init__(self, name, age):
self.name = name
self.age = age
def move(self):
print(str(self.name) + " moving")
def showing_age(self):
print(self.name + ' age: ' + self.age)
class Cat(Animal):
def __init__(self, name, age):
self.name = name
self.age = age
def sound(self):
print(str(self.name) + " meow")
def showing_age(self):
print(self.name + ' age: ' + self.age)
def print_hello_world():
print("Hello_World")
print("__name__ : " + str(__name__))
print_hello_world()
print("\n\n\n")
Tom = Cat('Tom', '28')
Tom.move()
Tom.showing_age()
Tom.sound()
print("\n\n\n")
Kevin = Animal('Kevin', '29')
Kevin.move()
Kevin.showing_age()
Kevin.sound()
"""
"""
```
### source
1. https://kopu.chat/2017/01/18/%e4%b8%80%e5%b0%8f%e6%99%82python%e5%85%a5%e9%96%80-part-1/
2. https://mofanpy.com/tutorials/python-basic/basic/
## python operators
### python Logical operators
```python=
a = 1
b = 2
result = (a == b)
if (result):
print("result is true") # false => this part is not going to execute
if (not result):
print("result is not true") # not false => this part is going to execute
if ((not result) and (a < 0)):
print("result is not true and a is less than 0") # not false but a > 0 => this part is not going to execute
if (result or (b > 0)):
print("result is true or b is more than 0") # false, however b > 0 => this part is going to execute
```
## if __name__ == '__main__':
file name: test.py
```python=
print(__name__)
print('I love Python')
def love():
print('In function love, Python is Good')
if __name__ == '__main__':
love()
print('I wrote python everyday')
```
```bash=
python3 test.py
<< output:
__main__
I love Python
In function love, Python is Good
I wrote python everyday
output:
```
file name: import_test.py
```python=
import test
```
```bash=
python3 import_test.py
<< output:
test
I love Python
output:
```
only if __name__ == __main__, code in if __name__ == __main__ will be executed
### source
1. http://hn28082251.blogspot.com/2019/05/python-if-name-main.html
## def __init__
```python=
class Animal():
def __init__(self, name):
self.name = name
Lucky = Animal("Lucky")
print(Lucky.name) # output: Lucky
Unlucky = Animal()
print(Unlucky.name) # output: TypeError: __init__() missing 1 required positional argument: 'name'
```
def __init__ always executes when the object is declared
### source
1. https://weilihmen.medium.com/%E9%97%9C%E6%96%BCpython%E7%9A%84%E9%A1%9E%E5%88%A5-class-%E5%9F%BA%E6%9C%AC%E7%AF%87-5468812c58f2
## class a(b):
To describe it simply, object a inherit attribute of object b
http://yltang.net/tutorial/python/15/
## python _ __
### _function (sample code with bug)
plus one underscore in front of name of function, that means other programs outside can not use this function
Common.py
```python=
def _gcd_core(a, b):
if a > b:
return a
else:
return b
def find_cd(a):
cd_list=[]
for x in range(1, (a + 1)):
ans = a % x
if ans == 0:
cd_list.append(x)
return cd_list
print(find_cd(30)) # output: [1, 2, 3, 5, 6, 10, 15, 30]
print(_gcd_core(30, 7)) # output: 30
```
test.py
```python=
from Common import *
find_cd(30) # output: [1, 2, 3, 5, 6, 10, 15, 30]
_gcd_code(30,7) # output:
"""
output:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name '_gcd_code' is not defined
"""
```
https://medium.com/bits-to-blocks/python%E4%B8%AD%E7%9A%84underscore-%E8%88%87-9b40caf32483
### reference
https://www.w3schools.com/python/python_operators.asp
## pack python code to .exe
### reference
https://kknews.cc/zh-tw/code/ab2oy5n.html
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