chapter1.md

Python note

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群集資料型態

len( ) 以一個int物件傳回資料項的長度

len((“one”,))

1

len(“one”)

3

len("automatically”)

13

list型態 有個append()方法，可以將一個物件附加至一個清單

就像這樣：

x = ["zebra",49,-897,"arrvark",200]
x.append("more")
x

['zebra', 49, -897, 'arrvark', 200, 'more’]

list型態 有 insert() 用於將一個資料項插入被給定的索引位置

還有 remove() 用於從被給定的索引位置移除一個資料項

python 的 索引是從 0 開始

x

['zebra', 49, -897, 'arrvark', 200, 'more’]

x[1]

49

x[1] = "forty nine"
x

['zebra', 'forty nine', -897, 'arrvark', 200, 'more’]

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雖然a與b是不同的物件(具有不同的身份)，但他們有相同的值，

所以他們是相等的。

a = "many paths"
b = "many paths"
a is b

False

a == b

True

隸屬運算符

對於序列或群集之類的資料型態，像是字串、清單和位元組，我們可以使使用 in 運算元來測試隸屬關係，使用 not in 來測試無隸屬關係：

 P = (4,"frog",9,-33,9,2)
 2 in P

True

phrase = "wild SWans by Jung Chang"
"J" in phrase

True

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邏輯運算符

短路表達式x AND y，事實上等價於條件語句：if x then y else false。短路表達式x OR y，則等價於條件語句：if x then true else y。

five = 5
two = 2
zero = 0
five and two

2

two and five

5

five and zero

0

five or two

5

two or five

2

zero or five

5

5 | 3

7

2&1

0

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if 陳述句

與其他語言不同的是Python使用縮排來表示它的區塊結構。

if lines <1000:
    print\("small"\)
elif lines <10000:
    print\("medium"\)
else:
    print("large")

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for...in陳述句

>>>for country in ["Denmark","Finland","Norway","Sweden"]:
       print\(country\)

Denmark

Finland

Norway

Sweden

>>> for letter in "ABCDEFGHIJKLMNOPQRSTUVWXYZ":    

       if letter in "AEIOU":

           print\(letter,"is vowel"\)

      else:

          print\(letter,"is a consonant"\)

A is vowel

B is a consonant

C is a consonant

D is a consonant

E is vowel

F is a consonant

G is a consonant

H is a consonant

I is vowel

J is a consonant

K is a consonant

L is a consonant

M is a consonant

N is a consonant

O is vowel

P is a consonant

Q is a consonant

R is a consonant

S is a consonant

T is a consonant

U is vowel

V is a consonant

W is a consonant

X is a consonant

Y is a consonant

Z is a consonant

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函式的建立與呼叫

    def get_int(msg):
        while True:
            try:
                i=int\(input\(msg\)\)
        return i
        except ValueError as err:
            print\(err\)

get_int(3)

3

get_int(q)

invalid literal for int() with base 10: 'get_int(q)’

計算成績

grades = [100, 100, 90, 40, 80, 100, 85, 70, 90, 65, 90, 85, 50.5]
def grades_sum(scores):
    total = 0
    for score in scores:
        total += score
    print total
    return total
grades_sum(grades)