複習一下我們昨天學到什麼¶
- python中任何東西都是個物件，每個物件都有它自己的型別（type）
- 常見的型別有int、float、string等等
- 除了int與float之間可以直接做運算，其他不同型別的物件彼此做運算時需要轉換型別。
- if ... elif ... else
In [ ]:
score = int(input("Enter your grade: "))
if score < 70:
print('D')
elif score >= 70:
print('C')
elif score >= 80:
print('B')
elif score >= 90:
print('A')
Index¶
- Composite data types (複合資料型態)
- Variables, Objects, and References
- Loop (迴圈): while、for
1. Composite data types (複合資料型態)¶
- list
- tuple
- dict
1.1 List：有順序的物件集合，具有索引特性，長度可變動。¶
In [1]:
a = []
numbers = [100, 200, 300, 400, 500]
fruit = ['apple', 'banana']
mixed = [1, 0.9, 'cat', [1, 2], fruit]
print(a,numbers, fruit, mixed)
[] [100, 200, 300, 400, 500] ['apple', 'banana'] [1, 0.9, 'cat', [1, 2], ['apple', 'banana']]
In [2]:
numbers = [100, 200, 300, 400, 500]
print(numbers[0])
print(numbers[1])
print(numbers[-1])
100 200 500
常見的運算方式¶
In [61]:
# example update
numbers = [1,2,3,4]
numbers[0] = 2
numbers[1] = 3
print(numbers)
[2, 3, 3, 4]
[i : j] 從 i 開始，遇到 j 結束¶
In [3]:
numbers = [100, 200, 300, 400, 500]
print(numbers)
print(numbers[1:3])
[100, 200, 300, 400, 500] [200, 300]
In [4]:
numbers = [100, 200, 300, 400, 500, 600, 700, 800]
print(numbers[1:8:2])
[200, 400, 600, 800]
In [5]:
numbers = [100, 200, 300, 400, 500, 600, 700, 800]
del[numbers[1:10:2]]
print(numbers)
print(300 in numbers)
print(400 not in numbers)
[100, 300, 500, 700] True True
In [57]:
# example condition
courses = ['Math', 'Chinese']
if 'Math' in courses:
print('Math')
if 'English' not in courses:
print('English')
Math English
In [64]:
a = [2, 4, 6]
b = [1, 3, 5, 7, 9]
print(a + b)
print(a * 3 + b * 2)
c = [1]*10
print(c)
print(len(c))
print(b)
# print(max(b))
# print(min(b))
[2, 4, 6, 1, 3, 5, 7, 9] [2, 4, 6, 2, 4, 6, 2, 4, 6, 1, 3, 5, 7, 9, 1, 3, 5, 7, 9] [1, 1, 1, 1, 1, 1, 1, 1, 1, 1] 10 [1, 3, 5, 7, 9]
In [ ]:
# exmaple delete
numbers = [1, 2, 3, 4, 5]
del numbers[0]
print(numbers)
del numbers[2]
print(numbers)
del numbers[1:2]
print(numbers)
In [74]:
# example
num = [1,2,3,4]
num.append(5)
print(num)
num.pop()
print(num)
num.reverse()
print(num)
num.sort()
print(num)
[1, 2, 3, 4, 5] [1, 2, 3, 4] [4, 3, 2, 1] [1, 2, 3, 4]
1.2 tuple：就像是list，不過list賦值之後可以更改，但是tuple不行。¶
In [7]:
a = (1, 2, -1.2, 'hi')
print(a)
print(type(a))
(1, 2, -1.2, 'hi') <class 'tuple'>
In [8]:
fruit = ('apple', 'banana', 'grape', 'watermelon')
fruit = fruit + ('guava', '123')
print(fruit)
('apple', 'banana', 'grape', 'watermelon', 'guava', '123')
為什麼要加逗號？¶
In [9]:
a = (1)
print(type(a))
b = (1,)
print(type(b))
c = (1, 2)
print(type(c))
<class 'int'> <class 'tuple'> <class 'tuple'>
In [10]:
## 切記!有更動到值的運算都不能使用
In [11]:
number = (1, 2, 3)
# number[0] = 5
In [12]:
number = (1, 2, 3)
number = (4, 5, 6)
print(number)
(4, 5, 6)
In [13]:
number = [1, 2, 3]
number[0] = 4
number[1] = 5
number[2] = 6
1.3 字典(dictionary)¶
In [14]:
subject = ['Chinese', 'English', 'Math', 'History', 'Physics', 'Chemistry']
score = [98, 65, 87, 77, 50, 88]
ind = subject.index('Physics')
print("Physics score = ", score[ind])
Physics score = 50
字典的出現，使我們更方便取得對應的值。
In [15]:
grade = {
'Chinese' : 98,
'English' : 65,
'Math' : 87,
'History' : 77,
'Physics' : 50,
'Chemistry' : 88
}
print("Physics score = ", grade['Physics'])
Physics score = 50
In [17]:
grade = {
'Chinese' : 98,
'English' : 65,
}
In [ ]:
## Add
print(grade)
grade['Math'] = 100
print(grade)
In [ ]:
## Update
In [ ]:
print(grade)
grade['English'] = 95
print(grade)
In [19]:
## key 與 value 可以為任意型態
a = {
0 : 'Hi!',
'Apple' : 12.3,
}
print(a)
print(a['Apple'])
{0: 'Hi!', 'Apple': 12.3}
12.3
2. Variables, Objects, and References¶
Recap: What is an object ?¶
Everything in Python is an object !!!¶
Built-in Types Object example¶
In [ ]:
# Number
12 # integer
12.5 # float-point
-12.5 # negative
# String
'Hello Word'
# list
[1, 2, 3, 4]
In [ ]:
# variable a, object
a = 3
a = 'Hello World'
Variables (i.e. name)¶
Variables are created when assigned, can reference any type of object, and must be assigned before they are referenced.
- Variable creation
- Variable types
- Variable use
In [ ]:
a = 3 # Assign a name to an object
# 1. Create an object to represent the value 3.
# 2. Create the variable a, if it does not yet exist.
# 3. Link the variable a to the new object 3.
Types Live with Objects, Not Variables¶
In [ ]:
a = 3 # It's an integer
a = 'spam' # Now it's a string
a = 1.23 # Now it's a floating point
Shared References and In-Place Changes¶
- immutable objects
- int, float, bool, str, etc.
- mutable objects
- list, set, dict, etc.
Objects are Garbage-Collected¶
Whenever a name is assigned to a new object, the space held by the prior object is reclaimed if it is not referenced by any other name or object.
In [ ]:
a = 3 # It's an integer
a = 'spam' # Now it's a string
In [ ]:
x = 42
x = 'shrubbery' # Reclaim 42 now (unless referenced elsewhere)
x = 3.1415 # Reclaim 'shrubbery' now
x = [1, 2, 3] # Reclaim 3.1415 now
Example 2.1¶
經過這三個statements, print(a)的結果為何？
In [ ]:
# example1
a = "Hello"
b = a
b = "World"
print(a)
In [52]:
# answer
a = "Hello"
b = a
b = "World"
print(a)
Hello
Example 2.2¶
經過這三個statements, print(a)的結果為何？
In [ ]:
# example
a = ["Hello"]
b = a
b[0] = "World"
print(a)
In [53]:
# answer
a = ["Hello"]
b = a
b[0] = "World"
print(a)
['World']
3. Loop (迴圈)¶
- 3.1 While
- 3.2 Nested loop - While
- 3.3 For
- 3.4 Nested loop - For
3.1 While¶
In [20]:
a = 1
while a < 100:
print(a, end = ' ')
a += 2
print("end")
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 95 97 99 end
把小於10的奇數印出來¶
-引用自In [ ]:
total = 1 + 2 + 3 + 4 + 5 + 6
太累了!!¶
使用迴圈！¶
In [ ]:
n = 100
iterate = 0
while iterate != n:
iterate += 1
print(iterate, end=' ')
In [45]:
n = 100
iterate = 0
total = 0
while iterate != n:
iterate += 1
total += iterate
print(total)
5050
In [ ]:
a = 5
while a < 7:
if (a % 2 == 0):
print(a, "is even")
else:
print(a, "is odd")
a += 1
example 3.1.2: 欲求 1~1000 中可以整除11的最大數¶
In [ ]:
n = 0
ans = 0
while n <= 1000:
if (n % 11 == 0):
ans = n
n += 1
print(ans)
In [46]:
n = 1000
flag = True
while n > 0:
if (n % 11 == 0) and flag:
print("correct", n)
flag = False
break
print(n)
n -= 1
1000 999 998 997 996 995 994 993 992 991 correct 990
In [ ]:
n = 1000
while n > 0:
if (n % 11 == 0):
print("correct", n)
break
n -= 1
print(n)
"continue" : 省略下方迴圈區塊內的程式碼，進行迴圈的下一回合。¶
In [1]:
n = 10
while n > 0:
if n % 2 == 0:
print(n, "is even.")
n -= 1
continue
print(n, "is odd.")
n -= 1
print("End")
10 is even. 9 is odd. 8 is even. 7 is odd. 6 is even. 5 is odd. 4 is even. 3 is odd. 2 is even. 1 is odd. End
我想印 99乘法表¶
In [5]:
i = 1
while i < 10:
print(i, '*', 1, '=', i * 1, sep='', end='\t')
print(i, '*', 2, '=', i * 2, sep='', end='\t')
print(i, '*', 3, '=', i * 3, sep='', end='\t')
print(i, '*', 4, '=', i * 4, sep='', end='\t')
print(i, '*', 5, '=', i * 5, sep='', end='\t')
print(i, '*', 6, '=', i * 6, sep='', end='\t')
print(i, '*', 7, '=', i * 7, sep='', end='\t')
print(i, '*', 8, '=', i * 8, sep='', end='\t')
print(i, '*', 9, '=', i * 9, sep='', end='\n')
i += 1
1*1=1 1*2=2 1*3=3 1*4=4 1*5=5 1*6=6 1*7=7 1*8=8 1*9=9 2*1=2 2*2=4 2*3=6 2*4=8 2*5=10 2*6=12 2*7=14 2*8=16 2*9=18 3*1=3 3*2=6 3*3=9 3*4=12 3*5=15 3*6=18 3*7=21 3*8=24 3*9=27 4*1=4 4*2=8 4*3=12 4*4=16 4*5=20 4*6=24 4*7=28 4*8=32 4*9=36 5*1=5 5*2=10 5*3=15 5*4=20 5*5=25 5*6=30 5*7=35 5*8=40 5*9=45 6*1=6 6*2=12 6*3=18 6*4=24 6*5=30 6*6=36 6*7=42 6*8=48 6*9=54 7*1=7 7*2=14 7*3=21 7*4=28 7*5=35 7*6=42 7*7=49 7*8=56 7*9=63 8*1=8 8*2=16 8*3=24 8*4=32 8*5=40 8*6=48 8*7=56 8*8=64 8*9=72 9*1=9 9*2=18 9*3=27 9*4=36 9*5=45 9*6=54 9*7=63 9*8=72 9*9=81
如果今天是99*99乘法表呢？¶
3.2 巢狀迴圈(nested loop) - while¶
In [ ]:
i = 1 # 被乘數
j = 1 # 乘數
while i <= 9:
while j <= 9:
print(i, '*', j, '=', i* j, sep='', end='\t')
j += 1
print("")
j = 1
i += 1
課堂練習 － 思考一下 改變n的值會發生什麼事?¶
In [7]:
n = 9
i = 1
j = 1
while i <= n:
while j <= 5:
print(i, '*', j, '=', i* j, sep='', end='\t')
j += 1
print("")
j = 1
i += 1
1*1=1 1*2=2 1*3=3 1*4=4 1*5=5 2*1=2 2*2=4 2*3=6 2*4=8 2*5=10 3*1=3 3*2=6 3*3=9 3*4=12 3*5=15 4*1=4 4*2=8 4*3=12 4*4=16 4*5=20 5*1=5 5*2=10 5*3=15 5*4=20 5*5=25 6*1=6 6*2=12 6*3=18 6*4=24 6*5=30 7*1=7 7*2=14 7*3=21 7*4=28 7*5=35 8*1=8 8*2=16 8*3=24 8*4=32 8*5=40 9*1=9 9*2=18 9*3=27 9*4=36 9*5=45
In [8]:
n = 9
i = 1
j = 1
while i <= n:
while j <= n:
print(i, '*', j, '=', i* j, sep='', end='\t')
j += 1
print("")
j = 1
i += 1
1*1=1 1*2=2 1*3=3 1*4=4 1*5=5 1*6=6 1*7=7 1*8=8 1*9=9 2*1=2 2*2=4 2*3=6 2*4=8 2*5=10 2*6=12 2*7=14 2*8=16 2*9=18 3*1=3 3*2=6 3*3=9 3*4=12 3*5=15 3*6=18 3*7=21 3*8=24 3*9=27 4*1=4 4*2=8 4*3=12 4*4=16 4*5=20 4*6=24 4*7=28 4*8=32 4*9=36 5*1=5 5*2=10 5*3=15 5*4=20 5*5=25 5*6=30 5*7=35 5*8=40 5*9=45 6*1=6 6*2=12 6*3=18 6*4=24 6*5=30 6*6=36 6*7=42 6*8=48 6*9=54 7*1=7 7*2=14 7*3=21 7*4=28 7*5=35 7*6=42 7*7=49 7*8=56 7*9=63 8*1=8 8*2=16 8*3=24 8*4=32 8*5=40 8*6=48 8*7=56 8*8=64 8*9=72 9*1=9 9*2=18 9*3=27 9*4=36 9*5=45 9*6=54 9*7=63 9*8=72 9*9=81
In [9]:
i = 1
j = 1
while i <= 9:
while j <= 9:
if i*j < 50:
print(i, '*', j, '=', i* j, sep='', end='\t')
j += 1
print("")
j = 1
i += 1
1*1=1 1*2=2 1*3=3 1*4=4 1*5=5 1*6=6 1*7=7 1*8=8 1*9=9 2*1=2 2*2=4 2*3=6 2*4=8 2*5=10 2*6=12 2*7=14 2*8=16 2*9=18 3*1=3 3*2=6 3*3=9 3*4=12 3*5=15 3*6=18 3*7=21 3*8=24 3*9=27 4*1=4 4*2=8 4*3=12 4*4=16 4*5=20 4*6=24 4*7=28 4*8=32 4*9=36 5*1=5 5*2=10 5*3=15 5*4=20 5*5=25 5*6=30 5*7=35 5*8=40 5*9=45 6*1=6 6*2=12 6*3=18 6*4=24 6*5=30 6*6=36 6*7=42 6*8=48 7*1=7 7*2=14 7*3=21 7*4=28 7*5=35 7*6=42 7*7=49 8*1=8 8*2=16 8*3=24 8*4=32 8*5=40 8*6=48 9*1=9 9*2=18 9*3=27 9*4=36 9*5=45
In [10]:
i = 1
j = 1
while i <= 9:
while j <= 9:
if i*j > 50:
break
print(i, '*', j, '=', i* j, sep='', end='\t')
j += 1
print('')
j = 1
i += 1
1*1=1 1*2=2 1*3=3 1*4=4 1*5=5 1*6=6 1*7=7 1*8=8 1*9=9 2*1=2 2*2=4 2*3=6 2*4=8 2*5=10 2*6=12 2*7=14 2*8=16 2*9=18 3*1=3 3*2=6 3*3=9 3*4=12 3*5=15 3*6=18 3*7=21 3*8=24 3*9=27 4*1=4 4*2=8 4*3=12 4*4=16 4*5=20 4*6=24 4*7=28 4*8=32 4*9=36 5*1=5 5*2=10 5*3=15 5*4=20 5*5=25 5*6=30 5*7=35 5*8=40 5*9=45 6*1=6 6*2=12 6*3=18 6*4=24 6*5=30 6*6=36 6*7=42 6*8=48 7*1=7 7*2=14 7*3=21 7*4=28 7*5=35 7*6=42 7*7=49 8*1=8 8*2=16 8*3=24 8*4=32 8*5=40 8*6=48 9*1=9 9*2=18 9*3=27 9*4=36 9*5=45
若是使用 Terminal 請按Ctrl+c 強制停止¶
程式沒辦法結束¶
如何避免¶
- 使用迴圈時，確認迴圈會有結束的時候(變數起始值、累加、判斷..等)
- 使用 while True: 時，一定要有break，且確保會執行到break
3.3 for loop¶
In [11]:
range(1, 10)
Out[11]:
range(1, 10)
In [12]:
type(range(1, 10))
Out[12]:
range
In [14]:
for i in range(10):
print(i, end=' ')
0 1 2 3 4 5 6 7 8 9
In [ ]:
for i in range(2, 10, 2):
print(i, end=' ')
example 3.3.1: 從1加到100¶
In [16]:
total = 0
for i in range(101):
total += i
print(total)
5050
In [17]:
n = 1
total = 0
while n <= 100:
total += n
n += 1
print(total)
5050
example 3.3.2: for (with list)¶
In [20]:
fruit = ['apple', 'banana', 'grape', 'watermelon']
for i in fruit:
print(i, end=' ')
apple banana grape watermelon
In [21]:
prime = [2, 3, 5, 7, 11]
for i in prime:
print(i, end=' ')
2 3 5 7 11
example 3.3.3: for with string¶
In [23]:
fruit = 'Apple'
for i in fruit:
print(i)
A p p l e
example 3.3.4: 使用 break¶
In [25]:
for i in range(1000,0,-1):
if (i % 11 == 0):
print(i)
break
990
example 3.3.5: 使用 continue¶
In [26]:
for i in range(0,11):
if(i % 2 == 0):
print(i, "is even.")
continue
print(i, "is odd.")
0 is even. 1 is odd. 2 is even. 3 is odd. 4 is even. 5 is odd. 6 is even. 7 is odd. 8 is even. 9 is odd. 10 is even.
example 3.3.6: 找出list中的最大值¶
In [27]:
a = [10, 2, 8, 15, 21, 1]
maximum = 0
for i in a:
if maximum < i:
maximum = i
print(maximum)
21
example 3.3.7 用for loop完成 象限判斷¶
In [28]:
A = [-1, -10]
B = [5, -5]
C = [1, 1]
D = [-2, 3]
dots = [
['A', A],
['B', B],
['C', C],
['D', D]
]
for i in dots:
print(i[0], "is in", end=' ')
if i[1][0] > 0 and i[1][1] > 0:
print("I")
elif i[1][0] < 0 and i[1][1] > 0:
print("II")
elif i[1][0] < 0 and i[1][1] < 0:
print("III")
elif i[1][0] > 0 and i[1][1] < 0:
print("IV")
A is in III B is in IV C is in I D is in II
3.4 巢狀迴圈(nested loop) - for¶
example 3.4.1 印出99乘法表¶
In [31]:
n = 10
for i in range(1, n):
for j in range(1, n):
print(i, '*', j, '=', i* j, sep='', end='\t')
print("")
1*1=1 1*2=2 1*3=3 1*4=4 1*5=5 1*6=6 1*7=7 1*8=8 1*9=9 2*1=2 2*2=4 2*3=6 2*4=8 2*5=10 2*6=12 2*7=14 2*8=16 2*9=18 3*1=3 3*2=6 3*3=9 3*4=12 3*5=15 3*6=18 3*7=21 3*8=24 3*9=27 4*1=4 4*2=8 4*3=12 4*4=16 4*5=20 4*6=24 4*7=28 4*8=32 4*9=36 5*1=5 5*2=10 5*3=15 5*4=20 5*5=25 5*6=30 5*7=35 5*8=40 5*9=45 6*1=6 6*2=12 6*3=18 6*4=24 6*5=30 6*6=36 6*7=42 6*8=48 6*9=54 7*1=7 7*2=14 7*3=21 7*4=28 7*5=35 7*6=42 7*7=49 7*8=56 7*9=63 8*1=8 8*2=16 8*3=24 8*4=32 8*5=40 8*6=48 8*7=56 8*8=64 8*9=72 9*1=9 9*2=18 9*3=27 9*4=36 9*5=45 9*6=54 9*7=63 9*8=72 9*9=81
example 3.4.2: 建立二維矩陣¶
In [34]:
n = 3
m = 3
table = []
for i in range(n):
table.append([0] * 3)
print(table)
[[0, 0, 0], [0, 0, 0], [0, 0, 0]]
In [24]:
empty = []
empty.append(1)
print(empty)
empty.append([0] * 3)
print(empty)
[1] [1, [0, 0, 0]]
In [47]:
n = 3
m = 3
table = []
for i in range(n):
table.append([0] * 3)
print("Initialize : ",table)
for i in range(n):
table[0][i] = i+1
table[1][i] = (i+1)**2
table[2][i] = (i+1)**3
print(table)
print(table)
Initialize : [[0, 0, 0], [0, 0, 0], [0, 0, 0]] [[1, 0, 0], [1, 0, 0], [1, 0, 0]] [[1, 2, 0], [1, 4, 0], [1, 8, 0]] [[1, 2, 3], [1, 4, 9], [1, 8, 27]] [[1, 2, 3], [1, 4, 9], [1, 8, 27]]
example 3.4.3 把99乘法表的值存起來¶
In [35]:
n = 9
m = 9
mul_table = []
for i in range(n):
mul_table.append([0] * m)
print(mul_table)
for i in range(1, 10):
for j in range(1, 10):
mul_table[i-1][j-1] = i*j
print(mul_table[i-1])
[[0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0]] [1, 2, 3, 4, 5, 6, 7, 8, 9] [2, 4, 6, 8, 10, 12, 14, 16, 18] [3, 6, 9, 12, 15, 18, 21, 24, 27] [4, 8, 12, 16, 20, 24, 28, 32, 36] [5, 10, 15, 20, 25, 30, 35, 40, 45] [6, 12, 18, 24, 30, 36, 42, 48, 54] [7, 14, 21, 28, 35, 42, 49, 56, 63] [8, 16, 24, 32, 40, 48, 56, 64, 72] [9, 18, 27, 36, 45, 54, 63, 72, 81]
[CodingX] Lesson 03 - Python_Basic(II) by Kun-Ta Chuang Advanced Network Database Laboratory Dept. of Computer Science and Information Engineering National Cheng Kung University