Python note
===
```python=
exit(0) 強制離開
print(f'{(7.0/2.0):.2f}')
or
print('{:.2f}'.format(7.0/2.0))
輸出自定義浮點數
if __name__ == '__main__':
此區塊只有當作檔案時候才會執行，當作模組不會執行。
print('hello\nworld')
顯示包含跳脫字元
print(r'hello\nworld')
忽略跳脫字元
type()看型別
id() 看記憶體位置
chr() 數字轉字元
ord() 字元轉數字
len() 看長度
int() 轉成整數
input() 輸入
print() 顯示
as 關鍵字代表 alias
字串
a = a[::-1] 做 reverse 反向字串
字串內取代 replace
a = a.replace('a', 'b')
[] 代表 list 的意思，可以增加跟移除
.append() 增加
.append([x, y, z]) 增加一個 list 到 list 內
.extend([x,y]) 增加 x 和 y 元素到 list 內
.insert(i, x) 指定第某個位置插入
.remove(x) 移除某個值
.pop() 移除最後一個
.pop(N) 第N個移除
.sort() 排序
.sort(reverse = True) 反轉排序
.sort(key = str.upper) 大寫排序
.sort(key = str.lower) 小寫排序
.reverse() 反轉順序
.index(N) 指出第N個
.count(x) 計算出共有幾個
刪除重覆的
list2 = []
for i in list1:
if i not in list2:
list2.append(i)
max(list) 求最大的
min(list) 求最小的
sum(list) 求和
any(list) 如果都是 0 才會 False
all(list) 有一個 0 的就會 False
將 list 都轉成 int
line = list(map(int, line))
或
line = [int(i) for i in line]
注意:
map(function, iterable) 將 function 用於 iterable 的每個元素
from collections import namedtuple
Data = namedtunple('Data', ['attribute1', 'attribute2', 'attribute3'])
storage = Data('intel', 'AMD', 'Apple')
print(Data.attribute1)
set([1,2,3]) = {1,2,3} 是 set 的兩種表達方式，沒有順序而且是唯一性
sorted() 排序，可以對 list 跟 dict 使用
sorted([1,2,3], reverse= True) 逆向排序
new_list = sorted(my_list, key = max) 小到大排序
set_a.intersection(set_b) 交集的列出
set_a.union(set_b) 所有的列出
set_a.difference(set_b) 只有遮罩
set_a.symmetric_difference(set_b) 遮罩後並加上沒有被遮罩的
dict_test = {
'key':value,
'key':value
}
dict_test = dict(name='XX', grade='OO')
dict_test['key'] = value 新增或異動
del dict_test['key'] 刪除 dictionary 的一筆資料
for i in dict_test:
print(f'{i} | {dict_test[i]}')
sort key 印出 key 跟 value (dictionary)
for i in sorted(dict_test):
print((i, dict_test[i]), end = ' ')
或
[(k, d[k]) for k in sorted(d.keys())]
sort value 印出 key 跟 value (dictionary)
print(sorted(dict_test.items(), key = lambda token:(token[1], token[0])))
或
[v for v in sorted(d.values())]
for i in line:
token = i.split(':')
dict_test[token[0]] = token[1] 做出一個 dict
test = dict_test.get(key) 用 dict 取值
test = dict_test[key]
for key in data: 用 dict 做統計，get 找 key 如果沒有就回傳第二個參數
dict_test[key] = dict_test.get(key, 0) + 1
print(f'{ToStringPart} is test') 將 {} 內的東西變成字串
或是使用運算
print(f'{2*2=}') 顯示出 2*2=4
name = 'apple'
print(f'{names}') 顯示出 string
number = 10
print(f'{number:d}') 顯示出十進制
print(f'{number:b}') 顯示出二進制
print(f'{number:x}') 顯示出十六進制小寫
print(f'{number:X}') 顯示出十六進制大寫
print(f'{number:e}') 顯示出科學表示進制
print(f'{number:f}') 顯示出浮點數
print(f'{number:.2f}') 顯示出浮點數小數後兩位
print(f'{number:03d}') 顯示出十進制三位
if z < x < y: 在 python 可以這樣設定，不需要用 and 去作連接
if a and b: 在 python 內，邏輯用小寫 and or not
if a or b:
if not a:
my_bool = True 在 python 內，布林使用第一字大寫
my_bool = False
membership 以 list 為例子
apple_list = ['macOS', 'iOS', 'iPadOS']
if 'iOS' in apple_list:
print("Yes")
membership 以 字串 為例子
str1 = 'apple is good'
if 'bird' in str1:
print('YES')
membership 只能找 key 不能找 value
my_dict = {}
my_dict = {'A': 1, 'B':2, 'C':3}
if 3 in my_dict:
print("YES")
可以用 is 或 is not 去判斷，通常使用 id() 去判斷
if x is y:
if x is not z:
三目運算
my_var = exp1 if (condition) else exp2
random.seed(value) 用 value 產生亂數
random.randint(0, 5) 產生亂數，範圍是 0 到 5
num *= x + y 代表 num = num * (x + y)
for loop:
for var in container: 普通 for loop
for c in container: for loop 用於 dict
print(f'{c} have value {container[c]}')
reversed() 反轉 container 順序
import edit_distance
字元變化量少於 2。
for name in name_list:
if edit_distance.distance(name, input_name) < 2:
print("less than 2")
----------------------------
def distance(a,b):
'''
Calculates the Levenshtein distance between a and b.
'''
n, m = len(a), len(b)
if n > m:
# Make sure n <= m, to use O(min(n,m)) space
a,b = b,a
n,m = m,n
current = range(n+1)
for i in range(1,m+1):
previous, current = current, [i]+[0]*n
for j in range(1,n+1):
add, delete = previous[j]+1, current[j-1]+1
change = previous[j-1]
if a[j-1] != b[i-1]:
change = change + 1
current[j] = min(add, delete, change)
return current[n]
----------------------------
nums = [4, 8, 10]
for index in range(len(nums)):
value = nums[index]
print(f'{index}:{value}')
for value in nums:
index = nums.index(value)
print(f'{index}:{value}')
for (index, value) in enumerate(nums):
print(f'{index}:{value}')
str = 'appleisgood'
x = str[5:8] x 就是 isg
print(f'{"hello":20}') 就是格式化 20 個空格，只放入 hello，左邊(文字靠左)
print(f'{50:20}') 就是格式化 20 個空格，只放入 50，右邊(數字靠右)
print(f'{"hello":<20}') 就是格式化 20 個空格，只放入 hello，靠左對齊
print(f'{"hello":>20}') 就是格式化 20 個空格，只放入 hello，靠又對齊
print(f'{"hello":^20}') 就是格式化 20 個空格，只放入 hello，至中對齊
print(f'{score:0>4}') 格式化後，靠右，顯示四個單位，其餘空間補0
print(f'{score:*>4}') 格式化後，靠右，顯示四個單位，其餘空間補*
str.find('xxx') 找目標位於第幾個
str.find('xxx', 2) 從第二個位置開始找目標
str.find('xxx', 2, 4) 從第二個位置開始找目標，停於第四個位置
str.rfind('xxx') 從尾部找
str.count('xxx') 計算有幾個目標
str.isalnum() 是否字母或數字
str.isdigit() 是否數字
str.islower() 是否小寫
str.isupper() 是否大寫
str.isspace() 是否空白
str.startswith() 是否以xxx開始
str.endswith() 是否以xxx結束
str.capitalize() 首字母大寫
str.lower() 都小寫
str.upper() 都大寫
str.strip() 空格移除
str.strip('\n') 移除換行
str.title() 第一個字
str.split() 以空白分割成 list
str.split('#') 以 # 分割成 list
str = '@'.join(list) 將 list 間隔用 @ 黏起來成一個字串
str = ''
for x in list: 用 for loop 把 list 內串成一個字串
str += x
def test_this_part(): 用於測試，傳出 None
pass
def neet_to_do(): 用於測試錯誤，會停住
raise NotImplementedError
def get_name():
global the_name # global 關鍵字，就是讓它成為全域變數
the_name = input('Enter the name')
print(globals()) 全域變數的 namespace
print(locals()) 區域變數的 namespace
def modify(num_list):
pass
modify(my_list[:]) 代表傳入一個 list 的 copy，這樣不會影響到原本的 list 值
def test_this(title, year, author):
支援參數指定，這樣可以不用按照順序
test_this(year = 2021, author = "Eric", title = "UCLA")
預設開一個 list，之後用預設會延續上一個
def append_list(value, my_list = []):
預設開一個空的，之後要指定才會延續上一個
def append_list(value, my_list = None):
if my_list == None:
my_list = []
args 參數變成一個 list container 來使用
def print_a(bread, meat, *args):
print_a('wheat', 'ham', 'apple', 'tomato')
kwargs 參數變成一個 dictionary container 來使用
def print_b(bread, meat, **kwargs):
print_b('wheat', 'ham', sauce1='test1', sauce2='test2')
return a, b 回傳一個 tuple a, b
return (a, b) 回傳一個 tuple a, b 這樣比較推薦，看起來比較清楚
return [a, b] 回傳一個 list a, b
docstrings 使用方法，單行就是 """ """ 同一行
多行就是，結尾會留一行空白。
help() 會將 docstrings 列出來
my_list[5] = [10] 在 list 第五個位置放上 10
my_list[len(my_list):] = [10]
就是在 list 最後自訂一個值，自訂的值外面是有 [] 包住。
list2 = list1 兩個指向同一個物件，會互相干擾。
list2 = list1[:] list2 是複製 list1 物件，互相不干擾
list2 = list1.copy() list2 是複製 list1 物件，互相不干擾
new_list = [expression for loop_variable_name in iterable]
new_list = [expression for loop_variable_name in iterable if condition]
import sys
program = sys.argv[0]
name = sys.argv[1]
age = int(sys.argv[2])
argparse and getopt 是參數研究
my_dict = {}
my_dict.clear() 清除所有
my_dict.setdefault('key', 'value') 新增
my_dict.get(key, default) 查 value，查不到回傳 default (通常是設為 0)
my_dict.update({'key':'value'}) 更新 key value，如果沒有就新增
my_dict.pop('key', default) 移除 key，查不到回傳 default (通常是 0)
my_dict.items() 回傳 key, value
my_dict.keys() 回傳 key
my_dict.values() 回傳 value
my_dict['key']
del my_dict['key']
my_dict2 = my_dict.copy()
my_dict = {'a':1, 'b':2}
if my_dict.__contains__('a'): 會顯示出 yes，如果改成 'c' 則會顯示出 no
print('Yes')
else:
print('No')
class Time: 建立一個類雛形與基礎的 constructor
gmt_offset = 0
def __init__(self):
self.hours = 0
self.minutes = 0
def __init__(self, hours = 0, minutes = 0): 初始化的 constructor
self.hours = hours
self.minutes = minutes
def __str__(self): 設計給 print 使用
return (f'{self.hours} and {self.minutes}')
time1 = Time() 使用一個物件，用類形成
time1.hours = 7
time1.minutes = 8
Time.gmt_offset = -8 這個會讓之後所有用到 Time() 物件有影響
print(time1) 直接顯示這個物件的字串
重載使用 overload
def __lt__(self, other): (<)
def __le__(self, other): (<=)
def __gt__(self, other): (>)
def __ge__(self, other): (>=)
def __eq__(self, other): (==)
def __ne__(self, other): (!=)
try: 這樣可以避免一些問題。
BLOCK
exception:
BLOCK
try: 這樣可以避免一些問題。
BLOCK
exception error_type1:
BLOCK
exception error_type2:
BLOCK
exception error_type3:
BLOCK
exception:
BLOCK
--------------------
def get_age():
age = int(input())
# TODO: Raise excpetion for invalid ages
if age < 18 or age > 75:
raise ValueError('Invalid age.')
return age
# TODO: Complete fat_burning_heart_rate() function
def fat_burning_heart_rate(age):
heart_rate = (220 - age) * 0.7
return heart_rate
if __name__ == "__main__":
# TODO: Modify to call get_age() and fat_burning_heart_rate()
# and handle the exception
try:
age = get_age()
print(f'Fat burning heart rate for a {age} year-old: {fat_burning_heart_rate(age):.1f} bpm')
except ValueError as e:
print(e)
print('Could not calculate heart rate info.')
--------------------
try: 這樣可以避免一些問題。
BLOCK
exception (error_type1, error_type2):
BLOCK
exception (error_type3, error_type4):
BLOCK
Error type: https://docs.python.org/3/library/exceptions.html
EOFError: end of file
KeyError: dictionary key
ZeroDivisionError: divide by zero
ValueError: invalid value
IndexError: index out of bounds
AttributeError: does not exist in an imported module
try:
weight = int(input())
if weight < 0:
raise ValueError('xxx') 自訂文字，可以把 raise 想成 goto
except ValueError as e:
print(e) 顯示自訂的文字
設定在方法內
def get_weight():
weight = int(input())
if weight < 0:
raise ValueError('Invalid weight')
return weight
try:
weight = get_weight() 方法出現問題會直接跳出來
print(weight)
except ValueError as e:
print(e)
使用最後 finally，一定會執行的
try:
BLOCK
except:
BLOCK
finally:
BLOCK
read file 讀檔案配合 try 跟 except
1.txt:
100
200
300
1.py:
nums = []
rd_nums = -1
my_file = input('Enter file name: ')
try:
print('Opening', my_file)
rd_nums = open(my_file, 'r') # Might cause IOError
for line in rd_nums:
nums.append(int(line)) # Might cause ValueError
except IOError:
print('Could not find', my_file)
except ValueError:
print('Could not read number from', my_file)
finally:
print('Closing', my_file)
if rd_nums != -1:
rd_nums.close()
print('Numbers found:', ' '.join([str(n) for n in nums]))
客製化 exception type:
1.py:
class LessThanZeroError(Exception): 客製化的 exception
def __init__(self, value):
self.value = value
my_num = int(input('Enter number: '))
if my_num < 0:
raise LessThanZeroError('my_num must be greater than 0')
else:
print('my_num:', my_num)
偷懶的方法就是
class LessThanZeroError(Exception): 客製化的 exception
def __init__(self, value):
pass
import MODULE
from NAME import MODULE
md5 範例:
from hashlib import md5, sha1
text = input("Enter text to hash ('q' to quit): ")
while text != 'q':
algorithm = input('Enter algorithm (md5/sha1): ')
if algorithm == 'md5':
output = md5(text.encode('utf-8'))
elif algorithm == 'sha1':
output = sha1(text.encode('utf-8'))
else:
output = 'Invalid algorithm selection'
print('Hash value:', output.hexdigest())
text = input("\nEnter text to hash ('q' to quit): ")
測試是 module 或是 script
if __name__ == "__main__":
# file executed as a script
if __name__ == "MODULE_NAME"
# file executed as a module
https://docs.python.org/3/library/datetime.html
https://docs.python.org/3/library/random.html
https://docs.python.org/3/library/copy.html
https://docs.python.org/3/library/time.html
https://docs.python.org/3/library/math.html
https://docs.python.org/3/library/os.html
https://docs.python.org/3/library/sys.html
https://docs.python.org/3/library/pdb.html
https://docs.python.org/3/library/urllib.html
date practice:
import datetime
# Create a new date object representing the current date (May 30, 2016)
today = datetime.date.today()
days_from_now = int(input('Enter number of days from now: '))
# Create a new timedelta object that represents a difference in the
# number of days between dates.
day_difference = datetime.timedelta(days = days_from_now)
# Calculate new date
future_date = today + day_difference
print(days_from_now, 'days from now is', future_date.strftime('%B %d, %Y'))
deck:
import random
# Create a shuffled card deck with 4 suites of cards 2-10, and face cards
deck = [2, 3, 4, 5, 6, 7, 8, 9, 10, 'J', 'Q', 'K', 'A'] * 4
random.shuffle(deck)
num_drawn = 0
game_over = False
user_input = input("Press any key to draw a card ('q' to quit): ")
while user_input != 'q' and not game_over:
# Draw a random card, and remove card from the deck
card = random.choice(deck)
deck.remove(card)
num_drawn += 1
print('\nCard drawn:', card)
# Game is over if an ace was drawn
if card == 'A':
game_over = True
else:
user_input = input("Press any key to draw a card ('q' to quit): ")
if user_input == 'q':
print("\nGame was quit")
else:
print(num_drawn, 'card(s) were drawn to find an ace.')
檔案讀取:
f = open('FILE') 打開檔案成一個物件
text = f.read() 讀檔案成一個字串
text = f.read(512) 讀檔案上到 512 bytes
text = f.readline() 讀檔案只讀一行字串
text = f.readlines() 讀檔案成一個 list 的字串
print(text) 印出讀到的檔案
f.close() 關閉檔案
----
filename = input()
b1 = input()
b2 = input()
data = open(filename)
lines = data.readlines()
for i in lines:
i = i.replace('\n', '')
if i >= b1 and i <= b2:
print(i)
data.close()
----
f = open('FILE') 沒有參數，預設是 r
text = f.readlines()
for x in text:
print(x, end='')
f.close()
寫入:
f = open('FILE', 'w')
f.write('Example\n')
f.close()
寫入必須是字串，所以數字或是浮點數就要用 str() 去變成字串去寫入
import os
f = open('FILE', 'w')
f.write('Please\n')
f.flush()
os.fsync(f.fileno()) 通常 f.flush() 和 os.fsync(f.fileno()) 一起搭配
f.close()
# build a path string using current OS path separator
file_path = os.path.join('storage','log.txt')
# build a tuple (head and tail) means (path, fileName)
print(os.path.split(file_path))
# whether file exists
if (os.path.exists(file_path)):
# whether that is a file or directory
if (os.path.isfile(file_path)):
# bytes
print(os.path.getsize(file_path))
for dirname, subdirs, files in os.walk(path):
dirname 就是目前目錄
subdirs 子目錄
files 檔案
f = open('FILE', 'rb') 以二進制讀取
#creates a sequence of bytes by encoding the string using ASCII
my_str = b'this is a book'
bytes('this is a book', 'ascii')
import struct struct.pack 輸入數字轉2進制
print(struct.pack('>h', 5)) b'\x00\x05' 靠右
print(struct.pack('<h', 5)) b'\x05\x00' 靠左
print(struct.pack('>h', 256)) b'\x01\x00'
print(struct.pack('>hh', 5, 256)) b'\x00\x05\x01\x00'
h: 2 bytes
b: 1 byte
l: 4 bytes
s: a string
print(struct.unpack('>h', b'\x00\x05')) struct.unpack 輸入二進制轉數字
print(repr('\x00\x05')) 將進制轉成字串，可以輸出，否則無法輸出
command-line:
import sys
import os
if len(sys.argv) != 2:
print(f'Usage: {sys.argv[0]} input_file')
sys.exit(1) # 1 indicates error
print(f'Opening file {sys.argv[1]}.')
if not os.path.exists(sys.argv[1]): # Make sure file exists
print('File does not exist.')
sys.exit(1) # 1 indicates error
f = open(sys.argv[1], 'r')
# Input files should contain two integers on separate lines
print('Reading two integers.')
num1 = int(f.readline())
num2 = int(f.readline())
print(f'Closing file {sys.argv[1]}')
f.close() # Done with the file, so close it
print(f'\nnum1: {num1}')
print(f'num2: {num2}')
print(f'num1 + num2: {num1 + num2}')
1.txt:
100
200
with 的功能就是加強版的 open，因為執行完 block 會自動關閉
以前是
f = open(sys.argv[1], 'r+')
現在是
with open(sys.argv[1], 'r+') as f:
num1 = int(f.readline())
num2 = int(f.readline())
result = num1 + num2
f.write(str(result))
# 此程式結束這區快會自動 close
CSV example (comma separate value files):
讀取 csv 檔
import csv
with open('grades.csv', 'r') as c_file:
row_num = 1
data = csv.reader(c_file, delimiter = ',')
for row in data:
print(f'row{row_num}:', row)
row_num += 1
with open('file.csv', 'r') as c_file:
user_file = csv.reader(c_file, delimiter = ',')
for data in user_file:
for i in data:
print(i)
寫入 csv 檔
import csv
r1 = ['100', '50', '29']
r2 = ['76', '32', '330']
with open('test.csv', 'w') as c_file:
x = csv.writer(c_file)
x.writerow(r1) # 寫入單行
x.writerow(r2)
x.writerow('') # 寫入空行(換行)
x.writerows([r1, r2]) # 寫入多行，但是用 list 方式寫入
計算 csv 檔
grades.csv:
name,hw1,hw2,midterm,final
Petr Little,9,8,85,78
Sam Tarley,10,10,99,100
Joff King,4,2,55,61
csv_example3.py:
import csv
# Dictionary that maps student names to a list of scores
grades = {}
# Use with statement to guarantee file closure
with open('grades.csv', 'r') as csvfile:
grades_reader = csv.reader(csvfile, delimiter=',')
first_row = True
for row in grades_reader:
# Skip the first row with column names
if first_row:
first_row = False
continue
## Calculate final student grade ##
name = row[0]
# Convert score strings into floats
scores = [float(cell) for cell in row[1:]]
hw1_weighted = scores[0]/10 * 0.05
hw2_weighted = scores[1]/10 * 0.05
mid_weighted = scores[2]/100 * 0.40
fin_weighted = scores[3]/100 * 0.50
result = hw1_weighted + hw2_weighted + mid_weighted + fin_weighted
grades[name] = result * 100
for student, score in grades.items():
print(f'{student} earned {score:.1f}%')
繼承
derived class or inherit class:
class Item:
def __init__(self):
self.name = ''
self.quantity = 0
def set_name(self, nm):
self.name = nm
def set_quantity(self, qnty):
self.quantity = qnty
def display(self):
print(self.name, self.quantity)
class Produce(Item): # Derived from Item
def __init__(self):
Item.__init__(self) # Call base class constructor
self.expiration = ''
def set_expiration(self, expir):
self.expiration = expir
def get_expiration(self):
return self.expiration
item1 = Item()
item1.set_name('Smith Cereal')
item1.set_quantity(9)
item1.display()
item2 = Produce()
item2.set_name('Apples')
item2.set_quantity(40)
item2.set_expiration('May 5, 2012')
item2.display()
print(f'(Expires:({item2.get_expiration()}))')
-------
class Pet:
def __init__(self):
self.name = ''
self.age = 0
def print_info(self):
print('Pet Information:')
print(' Name:', self.name)
print(' Age:', self.age)
class Dog(Pet):
def __init__(self):
Pet.__init__(self)
self.breed = ''
def print_info(self):
Pet.print_info(self)
print(' Breed:', self.breed)
my_pet = Pet()
my_dog = Dog()
pet_name = input()
pet_age = int(input())
dog_name = input()
dog_age = int(input())
dog_breed = input()
# TODO: Create generic pet (using pet_name, pet_age)
# and then call print_info()
my_pet.name = pet_name
my_pet.age = pet_age
my_pet.print_info()
# TODO: Create dog pet (using dog_name, dog_age, dog_breed)
# and then call print_info()
my_dog.name = dog_name
my_dog.age = dog_age
my_dog.breed = dog_breed
my_dog.print_info()
-------
has a 沒有繼承，is a 是有繼承
# 這個就是 has a，child object has a string object
class Child:
def __init__(self):
self.name = ''
self.birthdate = ''
self.schoolname = ''
--------------------------------
# 這個就是 is a，child object is a kind of person
class Person:
def __init__(self):
self.name = ''
self.birthdate = ''
class Child(Person):
def __init__(self):
Person.__init__(self)
self.schoolname = ''
多重繼承:
class BMW(vehicle, person):
--------------------------------
class Artist:
# TODO: Define constructor with parameters to initialize
# instance attributes
# (name, birth_year, death_year)
def __init__(self, name = 'None', birth_year = 0, death_year = 0):
self.name = name
self.birth_year = birth_year
self.death_year = death_year
# TODO: Define print_info() method.
# If death_year is -1, only print birth_year
def print_info(self):
if self.death_year == -1:
print(f'Artist: {self.name}, born {self.birth_year}')
else:
age = self.birth_year}-{self.death_year
print(f'Artist: {self.name} ({age})')
class Artwork:
# TODO: Define constructor with parameters to initialize
# instance attributes
# (title, year_created, artist) # 繼承
def __init__(self, title='None', year_created=0, artist=Artist()):
self.title = title
self.year_created = year_created
self.artist = artist
# TODO: Define print_info() method
def print_info(self):
self.artist.print_info()
print(f'Title: {self.title}, {self.year_created}')
--------------------------------
recursive:
def print_num_pattern(num1, num2):
if num1 <= 0:
print(num1, end = ' ')
return
print(num1, end = ' ')
print_num_pattern(num1 - num2, num2)
print(num1, end = ' ')
if __name__ == "__main__":
num1 = int(input())
num2 = int(input())
print_num_pattern(num1, num2)
--------------------------------
sort:
def selection_sort_descend_trace(numbers):
for i in range(len(numbers) - 1):
max_num = max(numbers[i:])
index = numbers.index(max(numbers[i:]))
tmp = numbers[i]
numbers[i] = max_num
numbers[index] = tmp
for j in numbers:
print(j, end = ' ')
print()
if __name__ == "__main__":
nlist = input().split()
numbers = [int(i) for i in nlist]
selection_sort_descend_trace(numbers)
--------------------------------
quick sort:
# Global variable
num_calls = 0
# TODO: Write the partitioning algorithm - pick the middle element
# as the pivot, compare the values using two index
# variables l and h (low and high), initialized to the left
# and right sides of the current elements being sorted,
# and determine if a swap is necessary
def partition(user_ids, i, k):
# Pick middle value as pivot
midpoint = i + (k - i) // 2
pivot = user_ids[midpoint]
# Initialize variables
done = False
l = i
h = k
while not done:
# Increment l while user_ids[l] < pivot
while user_ids[l] < pivot:
l = l + 1
# Decrement h while pivot < user_ids[h]
while pivot < user_ids[h]:
h = h - 1
# If there are zero or one items remaining,
# all items are partitioned. Return h
if l >= h:
done = True
else:
# Swap user_ids[l] and user_ids[h], update l and h
temp = user_ids[l]
user_ids[l] = user_ids[h]
user_ids[h] = temp
l = l + 1
h = h - 1
return h
# TODO: Write the quicksort algorithm that recursively
# sorts the low and high partitions.
# Add 1 to num_calls each time quisksort() is called
def quicksort(user_ids, i, k):
global num_calls
num_calls += 1
# Base case: If 1 or zero elements, partition is already sorted
if i >= k:
return
# Partition the list. Value j is the location of last
# element in low partition
j = partition(user_ids, i, k)
# Recursively sort low and high partitions
quicksort(user_ids, i, j)
quicksort(user_ids, j + 1, k)
return
if __name__ == "__main__":
user_ids = []
user_id = input()
while user_id != "-1":
user_ids.append(user_id)
user_id = input()
# Initial call to quicksort
quicksort(user_ids, 0, len(user_ids) - 1)
# Print number of calls to quicksort
print(num_calls)
# Print sorted user ids
for user_id in user_ids:
print(user_id)
--------------------------------
remove duplicate:
mylist = ["a", "b", "a", "c", "c"]
mylist = list(dict.fromkeys(mylist))
print(mylist)
--------------------------------
def all_permutations(permList, nameList):
size = len(nameList)
if size == 0:
for i in permList:
print(i, end = ' ')
print()
else:
for i in range(size):
newPerm = permList.copy()
newPerm.append(nameList[i])
newName = nameList.copy()
newName.pop(i)
all_permutations(newPerm, newName)
if __name__ == "__main__":
nameList = input().split()
permList = []
all_permutations(permList, nameList)
--------------------------------
import itertools as its # 用現成的工具
data = list(its.permutations([1,2,3]))
for i in data:
for j in list(i):
print(j, end = ' ')
print()
--------------------------------
unittest
方法 檢查項目
assertEqual(a, b) a == b
assertNotEqual(a, b) a != b
assertTrue(x) bool(x) is True
assertFalse(x) bool(x) is False
assertIs(a, b) a is b
assertIsNot(a, b) a is not b
assertIsNone(x) x is None
assertIsNotNone(x) x is not None
assertIn(a, b) a in b
assertNotIn(a, b) a not in b
assertAlmostEqual(a, b) round(a - b, 7) == 0 by default.
# assertAlmostEqual(first, second, places = 7, msg = None, delta = None)
assertGreater(a, b) a > b
assertGreaterEqual(a, b) a >= b
assertLess(a, b) a < b
assertLessEqual(a, b) a <= b
密技:
進制轉換
int('string', base)
a = 79
bin_a = bin(a)
print(bin_a) 0b1001111
print(int(bin_a, 2)) 79
oct_a = oct(a)
print(oct_a) 0o117
print(int(oct_a, 8)) 79
hex_a = hex(a)
print(hex_a) 0x4f
print(int(hex_a, 16)) 79
---
from math import factorial
factorial(10)
---
from math import sqrt
sqrt(100)
---
from time import sleep
sleep(10)
---
from math import pi
pi
---
def isprime(num):
for n in range(2, sqrt(num) + 1):
if num % n == 0:
return False
return True
---
ff = lambda a, b, c, d: a * b * c * d
相當於
def ff(a, b, c, d):
return a * b * c *d
print(ff(1,2,3,4))
```
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