Python × 資料分析¶

Loop & Conditional judgment¶

Kristen Chan¶

Agenda¶

Conditional judgment
Loops
- for
- while
- Nested loops
Loops & Conditional judgment
Loops II
- break
- continue

Conditional judgment¶

流程控制

語法 ( if/elif/else )

if expression1:
  statement
elif expression2:
  statement
elif expression3:
  statement 
else:
  statement

Conditional judgment¶

利用判斷式 if/elif/else 做出判斷¶

若某件事為真 ( True ) ，則做出對應動作。
if 是必備的
語法組合可分為：
- if：一種選項，滿足條件，才執行某動作
- if + else：兩種選項，滿足條件與其他狀況(不滿足條件)，各執行某動作
- if + elif：兩種選項，滿足各條件，各執行某動作
- if + elif + (elif)... + (else)：多種選項，滿足各條件，各執行某動作
可以搭配邏輯運算子 & (and) 、 | (or)

Conditional judgment¶

Example¶

if (a > b):
    print ("a is greater than b")
elif (a < b):
    print ("a is less than b")
else:
    print ("a is equal to b")

Conditional judgment¶

In [1]:

a = 100
b = 95

if (a > b):
    print ("a is greater than b")
elif (a < b):
    print ("a is less than b")
else:
    print ("a is equal to b")

a is greater than b

Note
¶

`in` 功能¶

某個元素是否在串列中

In [2]:

my_string = "Hello Python!!"

if "H" in my_string:
    print("Found ","H")
else :
    print("Not Found")

Found  H

Exercise
¶

Q. 利用 `in` 及 `if`/`else` 判斷式，判斷 fruit 中有沒有 `"apple"`¶

fruit = ['banana', 'Wax apple','cherry', 'coconut', 'jujube', 'durian', 'grape', 'grapefruit', 'guava', 'lemon', 'pineapple', 'Watermelon', 'Kiwi', 'Orange', 'Longan', 'Blueberry', 'Mango']

Answers
¶

In [3]:

fruit = ['banana', 'Wax apple','cherry', 'coconut', 'jujube', 'durian', 'grape', 'grapefruit', 'guava', 'lemon', 'pineapple', 'Watermelon', 'Kiwi', 'Orange', 'Longan', 'Blueberry', 'Mango']

In [4]:

if "apple" in fruit:
    print('I find apple!')
else:
    print('No apple.')

No apple.

Note
¶

若 in 後面放的是字串

"pineapple" or "Wax apple"

In [5]:

if "apple" in "pineapple":
    print('I find apple!')
else:
    print('No apple.')

I find apple!

In [6]:

if "apple" in "Wax apple":
    print('I find apple!')
else:
    print('No apple.')

I find apple!

Loop¶

Loop ( `for` )¶

做重複的事

語法

for iterating_var in sequence:
    statements

Loop ( `for` )¶

宣告一個 iterating_var (迭代變量)
宣告一個 sequence (迴圈要跑的範圍)
縮排並宣告 statements (每次迭代的時候要做什麼事)

Loop ( `for` )¶

Example¶

city = 'Taipei'

print(city[0])
T
print(city[1])
a
print(city[2])
i
print(city[3])
p
print(city[4])
e
print(city[5])
i

Loop ( `for` )¶

In [7]:

city = 'Taipei'
for i in city:
    print(i)

T
a
i
p
e
i

Exercise
¶

Q. 現在有一個未來一週 Taipei 的溫度，希望分別印出每一天的溫度¶

Temperature_Taipei = [22 , 24 , 19, 19, 30, 21, 25]

Answers
¶

逐一 `print` 出來¶

In [8]:

Temperature_Taipei = [22 , 24 , 19, 19, 30, 21, 25]

In [9]:

print(Temperature_Taipei[0])
print(Temperature_Taipei[1])
print(Temperature_Taipei[2])
print(Temperature_Taipei[3])
print(Temperature_Taipei[4])
print(Temperature_Taipei[5])
print(Temperature_Taipei[6])

Answers
¶

利用 `for`¶

In [10]:

Temperature_Taipei = [22 , 24 , 19, 19, 30, 21, 25]

In [11]:

for i in Temperature_Taipei:
    print(i)

Note
¶

`range ( )`¶

一個整數的序列
語法
```
range( start , stop , step )
```
start: 起始值
stop: 結束值
step: 差值

Note
¶

`range ( )`¶

In [12]:

print(range(10))

range(0, 10)

In [13]:

print(type(range(10)))

<class 'range'>

In [14]:

print(list(range(10)))

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

Note
¶

`range ( )`¶

In [15]:

print(list(range(0, 10)))

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

In [16]:

print(list(range(0, 10, 2)))

[0, 2, 4, 6, 8]

In [17]:

print(list(range(1, 6, 2)))

[1, 3, 5]

Loop ( `for` )¶

`for & range( )`¶

利用 for statements 和 range( )
依序輸出一個 -5 到 5 間隔 1 的數列中的每個 element

In [18]:

for i in range(5, -6 , -1):
    print(i)

Loop ( `for` )¶

`for & range( )`¶

利用 for statements 和 range( )
依序輸出一個 -5 到 5 間隔 1 的數列中的每個 element

In [19]:

for i in range(-5, 6, 1):
    print(i)

Loop ( `for` )¶

Method 1.¶

In [20]:

city = 'Taipei'
for i in city:
    print(i)

T
a
i
p
e
i

Loop ( `for` )¶

Method 2.¶

In [21]:

city = 'Taipei'
for i in range(0,len(city)):
    print(city[i])

T
a
i
p
e
i

Exercise
¶

Q. 依序印出 city_list 中的元素¶

city = ['Taipei', ['Taichung',22],  {'Kaohsiung':25}]

輸出不必是單一個值也可以是 list 或 dictionary

Answers
¶

Method 1.¶

In [22]:

city_list = ['Taipei', ['Taichung',22], {'Kaohsiung':25}]

In [23]:

city = ['Taipei', ['Taichung',22],  {'Kaohsiung':25}]
for i in city:
    print (i)

Taipei
['Taichung', 22]
{'Kaohsiung': 25}

Method 2.¶

In [24]:

city_list = ['Taipei', ['Taichung',22], {'Kaohsiung':25}]

In [25]:

for i in range(len(city_list)):
    print (city_list[i])

Taipei
['Taichung', 22]
{'Kaohsiung': 25}

Loop ( `for` )¶

語法
```
for iterating_var in sequence:
    statements
```
當 sequence 是一個 dictionary 會輸出 key 值

In [26]:

weather_dict = { 'Taipei':'rainy', 'Taichung':'cloudy' , 'Tainan':'sunny' , 'Kaohsiung':'sunny' }

In [27]:

print(weather_dict.keys())

dict_keys(['Taipei', 'Taichung', 'Tainan', 'Kaohsiung'])

In [28]:

#輸出 key 值
for i in weather_dict:
    print(i)

Taipei
Taichung
Tainan
Kaohsiung

Loop ( `for` )¶

語法
```
for iterating_var in sequence:
    statements
```
當 sequence 是一個 dictionary 想同時輸出 key,value 值

In [29]:

#輸出Key,Value
for (key, value) in weather_dict.items():
    print(key, ":", value)

Taipei : rainy
Taichung : cloudy
Tainan : sunny
Kaohsiung : sunny

Note
¶

`zip`¶

壓合兩個以上 list
- 長度相同

In [30]:

Week = ['SUN','MON','TUE','WED','THU','FRI','SAT']
Temperature_Taipei = [22 , 24 , 19, 19, 30, 21, 25]

In [31]:

list( zip( Week,Temperature_Taipei ) )

Out[31]:

[('SUN', 22),
 ('MON', 24),
 ('TUE', 19),
 ('WED', 19),
 ('THU', 30),
 ('FRI', 21),
 ('SAT', 25)]

Note
¶

`zip`¶

壓合兩個以上 list
- 長度不同

In [32]:

Week = ['SUN','MON','TUE','WED','THU','FRI','SAT']
Temperature_Taipei = [22 , 24 , 19, 19, 30, 21, 25]
Weather_Taipei = ['Yes','Yes','No']

In [33]:

list( zip( Week,Temperature_Taipei,Weather_Taipei ) )

Out[33]:

[('SUN', 22, 'Yes'), ('MON', 24, 'Yes'), ('TUE', 19, 'No')]

Loop ( `for` )¶

`for & zip( )`¶

利用 for statements 和 zip( )
同時取得兩個以上 sequence 的值

In [34]:

for week ,temperature in zip( Week,Temperature_Taipei ):
    print(week ,temperature)

SUN 22
MON 24
TUE 19
WED 19
THU 30
FRI 21
SAT 25

Note
¶

`enumerate`¶

同時取得 sequence 的索引值及其值

In [35]:

#不使用 enumerate
for index in range(len(Temperature_Taipei)): 
    print(index , ":", Temperature_Taipei[index])

Note
¶

`enumerate`¶

同時取得 sequence 的索引值及其值

In [36]:

#使用 enumerate
for index, temperature in enumerate(Temperature_Taipei): 
    print(index , ":", temperature)

Exercise
¶

Q. 利用 `for` statements 解決 `list` 不能逐項運算(element-wise) 的問題。希望將 Temperature_Taipei 中的所有溫度都轉成華氏¶

Temperature_Taipei = [22, 24, 19, 19, 30, 21, 25]

公式： $Fahrenheit = Celsius × (9/5) + 32$

Answers
¶

In [37]:

Temperature_Taipei = [22, 24, 19, 19, 30, 21, 25]

In [38]:

for i in Temperature_Taipei:
    print(i * (9/5) + 32)

71.6
75.2
66.2
66.2
86.0
69.80000000000001
77.0

Note
¶

將轉成華氏的結果存在一個 `list` 中¶

In [39]:

Temperature_Taipei = [22, 24, 19, 19, 30, 21, 25]

In [40]:

Temperature_Taipei_Fahrenheit = []
for i in Temperature_Taipei:
    Temperature_Taipei_Fahrenheit.append( i * (9/5) + 32 )
print(Temperature_Taipei_Fahrenheit)

[71.6, 75.2, 66.2, 66.2, 86.0, 69.80000000000001, 77.0]

Exercise
¶

Q. 利用 `for` 迴圈，計算 1 加到 100¶

公式： $ Total = \sum_{i=1}^{100} x_i $

提示1：可以利用 range來建立一個 1 到 100 的 list
提示2：可以跟 sum() 對答案

Answers
¶

`sum( )` 對答案¶

In [41]:

sum( range(1,101) )

Out[41]:

Method1.¶

In [42]:

total = 0
for i in range(1,101):
    total = total+i
print(total)

Answers
¶

`sum( )` 對答案¶

In [43]:

sum( range(1,101) )

Out[43]:

Method2.¶

In [44]:

total = 0
for i in range(1,101):
    total +=i
print(total)

Exercise
¶

Q. 利用 `for` 迴圈，計算 $5!$¶

公式： $ Factorial = \prod_{k=1}^{5} k $

Answers
¶

Method1.¶

In [45]:

factorial = 1
for i in range(1,6):
    factorial = factorial * i
print(factorial)

Method2.¶

In [46]:

factorial = 1
for i in range(1,6):
    factorial *= i
print(factorial)

Loop ( `while` )¶

做重複的事
語法
```
while expression:
    statements
```

Loop ( `while` )¶

宣告一個 expression (若條件為True就會執行)
縮排並宣告 statements (每次迭代的時候要做什麼事)

Loop ( `while` )¶

利用 `while` 迴圈，計算 1 加到 100¶

In [47]:

total = 0
i=0
while i < len(range(1,101)):
    total += range(1,101)[i]
    i += 1
print(total)

Loop ( Nested loops )¶

迴圈中還有一個迴圈

語法

for iterating_var in sequence:
  for iterating_var in sequence:
      statements
  statements

while expression:
  while expression:
      statements
  statements

Loop ( Nested loops )¶

利用 Nested loops 寫一個九九乘表¶

In [48]:

for i in range(1,10):
    for j in range(1,10):
        k=i*j
        print (k , end=' ')
    print()

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

Loop & Conditional judgment¶

利用 `if.. else..` 判斷 `list` 中元素的狀況¶

Exercise
¶

Q. 判斷未來 Taipei 一週天氣狀況，如果溫度小於 22 度就在家，否則就出門¶

Temperature_Taipei = [22, 24, 19, 19, 30, 21, 25]

Answers
¶

In [49]:

Temperature_Taipei = [22, 24, 19, 19, 30, 21, 25]

In [50]:

for i in Temperature_Taipei :
    if i <= 22:
        print('在家')
    else :
        print('出門')

在家
出門
在家
在家
出門
在家
出門

Loop & Conditional judgment¶

利用 `zip( )` 及 `if.. else..` 比較兩個 `list` 中元素的大小¶

In [51]:

Temperature_Taipei = [22 , 24 , 19, 19, 30, 21, 25]
Temperature_Taichung = [23 , 22 , 19, 20, 29, 19, 27]

In [52]:

for Taipei, Taichung in zip(Temperature_Taipei, Temperature_Taichung) :
    if Taipei > Taichung :
        print('Taipei 好熱')
    elif Taipei < Taichung :
        print('Taichung 好熱')    
    else :
        print('Taipei Taichung 都好熱')

Taichung 好熱
Taipei 好熱
Taipei Taichung 都好熱
Taichung 好熱
Taipei 好熱
Taipei 好熱
Taichung 好熱

Loops II¶

break : 離開
continue : 繼續

Loops II¶

Example¶

利用 for 及 break 試寫出一個判斷，如果遇到非 sunny 的天氣就停止 print ，否則則 print 出天氣狀況

Weather_Taipei = ['sunny','sunny','cloudy','sunny','rainy','cloudy','rainy']

In [53]:

Weather_Taipei = ['sunny','sunny','cloudy','sunny','rainy','cloudy','rainy']
for day in Weather_Taipei :
    if day !='sunny':
        break   
    else :
        print(day)

sunny
sunny

Loops II¶

Example¶

利用 for 及 continue 試寫出一個判斷， print 出所有 sunny 的天氣

Weather_Taipei = ['sunny','sunny','cloudy','sunny','rainy','cloudy','rainy']

In [54]:

Weather_Taipei = ['sunny','sunny','cloudy','sunny','rainy','cloudy','rainy']
for day in Weather_Taipei :
    if day !='sunny':
        continue  
    else :
        print(day)

sunny
sunny
sunny

Exercise
¶

Q. 現在有兩個 `list` 分別是未來一週 Taipei 的天氣以及星期，請找出未來一週天氣為 sunny 的星期¶

Week = ['SUN','MON','TUE','WED','THU','FRI','SAT']
Weather_Taipei = ['sunny','sunny','cloudy','sunny','rainy','cloudy','rainy']

Answers
¶

In [55]:

Week = ['SUN','MON','TUE','WED','THU','FRI','SAT']
Weather_Taipei = ['sunny','sunny','cloudy','sunny','rainy','cloudy','rainy']

In [56]:

for i , j in zip(Week,Weather_Taipei) :
    if j != 'sunny':
        continue 
    else :
        print(i)

SUN
MON
WED

提示：可以利用 zip

Python × 資料分析¶

Loop & Conditional judgment¶

Kristen Chan¶

Agenda¶

Conditional judgment¶

Conditional judgment¶

流程控制

語法 ( if/elif/else )

Conditional judgment¶

利用 判斷式 if/elif/else 做出判斷¶

Conditional judgment¶

Example¶

Conditional judgment¶

Note¶

in 功能¶

Exercise¶

Q. 利用 in 及 if/else 判斷式，判斷 fruit 中有沒有 "apple"¶

Answers¶

Note¶

Loop¶

Loop ( for )¶

做重複的事

語法

Loop ( for )¶

宣告一個 iterating_var (迭代變量)

宣告一個 sequence (迴圈要跑的範圍)

縮排並宣告 statements (每次迭代的時候要做什麼事)

Loop ( for )¶

Example¶

Loop ( for )¶

Exercise¶

Q. 現在有一個未來一週 Taipei 的溫度，希望分別印出每一天的溫度¶

Answers¶

逐一 print 出來¶

Answers¶

利用 for¶

Note¶

range ( )¶

Note¶

range ( )¶

Note¶

range ( )¶

Loop ( for )¶

for & range( )¶

Loop ( for )¶

for & range( )¶

Loop ( for )¶

Method 1.¶

Loop ( for )¶

Method 2.¶

Exercise¶

Q. 依序印出 city_list 中的元素¶

Answers¶

Method 1.¶

Method 2.¶

Loop ( for )¶

語法

Loop ( for )¶

語法

Note¶

zip¶

Note¶

zip¶

Loop ( for )¶

for & zip( )¶

Note¶

enumerate¶

Note¶

enumerate¶

Exercise¶

Q. 利用 for statements 解決 list 不能逐項運算(element-wise) 的問題。希望將 Temperature_Taipei 中的所有溫度都轉成華氏¶

Answers¶

Note¶

將轉成華氏的結果存在一個 list 中¶

Exercise¶

Q. 利用 for 迴圈，計算 1 加到 100¶

Answers¶

sum( ) 對答案¶

Method1.¶

Answers¶

利用判斷式 if/elif/else 做出判斷¶

Note
¶

`in` 功能¶

Exercise
¶

Q. 利用 `in` 及 `if`/`else` 判斷式，判斷 fruit 中有沒有 `"apple"`¶

Answers
¶

Note
¶

Loop ( `for` )¶

Loop ( `for` )¶

Loop ( `for` )¶

Loop ( `for` )¶

Exercise
¶

Answers
¶

逐一 `print` 出來¶

Answers
¶

利用 `for`¶

Note
¶

`range ( )`¶

Note
¶

`range ( )`¶

Note
¶

`range ( )`¶

Loop ( `for` )¶

`for & range( )`¶

Loop ( `for` )¶

`for & range( )`¶

Loop ( `for` )¶

Loop ( `for` )¶

Exercise
¶

Answers
¶

Loop ( `for` )¶

Loop ( `for` )¶

Note
¶

`zip`¶

Note
¶

`zip`¶

Loop ( `for` )¶

`for & zip( )`¶

Note
¶

`enumerate`¶

Note
¶

`enumerate`¶

Exercise
¶

Q. 利用 `for` statements 解決 `list` 不能逐項運算(element-wise) 的問題。希望將 Temperature_Taipei 中的所有溫度都轉成華氏¶

Answers
¶

Note
¶

將轉成華氏的結果存在一個 `list` 中¶

Exercise
¶

Q. 利用 `for` 迴圈，計算 1 加到 100¶

Answers
¶

`sum( )` 對答案¶

Answers
¶

`sum( )` 對答案¶

Exercise
¶

Q. 利用 `for` 迴圈，計算 $5!$¶

Answers
¶

Loop ( `while` )¶

Loop ( `while` )¶

Loop ( `while` )¶

利用 `while` 迴圈，計算 1 加到 100¶

利用 `if.. else..` 判斷 `list` 中元素的狀況¶

Exercise
¶

Answers
¶

利用 `zip( )` 及 `if.. else..` 比較兩個 `list` 中元素的大小¶

Exercise
¶

Q. 現在有兩個 `list` 分別是未來一週 Taipei 的天氣以及星期，請找出未來一週天氣為 sunny 的星期¶

Answers
¶