CH1
===
###### tags: `colde_garage_python_2019`
# 在開始之前你一定要知道的事...
1. python 非常注重縮排
2. python 是一種直譯式語言
3. python 變數的型別不是固定的
4. python 支援大數運算
## 範例
```python=
apple = 1
banana = 0
if apple > banana :
print("hello")
elif apple == 1:
print("apple")
else :
print("world")
print(apple)
print(banana)
```
```=
hello
1
0
```
# 如何使用python互動模式
1. Open termial
2. type "python3"
# Hello World
```python=
print("hello world")
```
# 註解
## 單行註解
```python=
#----單行註解------
```
## 多行註解
```python=
'''
多
行
註
解
'''
```
# 變數
## 變數型別
* 數值型態：int, float, bool
* 字串型態：str
## 如何使用
```python=
a = 1
b = 1.2
c = True
d = False
e = "hello"
f = 'a'
g = chr(96)
h = 1.5 + 3j
print( type(a) )
print( type(b) )
print( type(c) )
print( type(d) )
print( type(e) )
print( type(f) )
print( type(g) )
print( type(h) )
if type(d) == type(c):
print(c)
```
```=
<class 'int'>
<class 'float'>
<class 'bool'>
<class 'bool'>
<class 'str'>
<class 'str'>
<class 'str'>
<class 'complex'>
True
```
## 型別轉換
```python=
a = 1
b = float(a)
c = chr(100)
d = ord(c)
print(a, b, c, d)
```
```=
1 1.0 d 100
```
## 關於int
1. 不像 C 的 int 會溢位
2. 非常適合大數運算
# 運算子
* 算術運算子
+, -, *, /, %, //(取得整除的商數), ** (次方, 7**2 = 49)
* 關係運算子
==, !=, >, <, >=, <=
* 邏輯運算子
not, and, or
* 複合指定運算子
+=, -=, *=, /=, %=, //=, **=
# IO
## input
### python3
```python=
a = input("type what you want to talk: ")
b = input()
c = input()
print(type(a), type(b), type(c))
```
#### input
```
123
23.3
hello
```
#### output
```
<class 'str'> <class 'str'> <class 'str'>
```
### python2
```python=
a = input("type what you want to talk: ")
b = input()
c = input()
x = raw_input("type what you want to talk: ")
y = raw_input()
z = raw_input()
print(type(a), type(b), type(c))
print(type(x), type(y), type(z))
```
#### input
```=
123
23.3
"hello"
123
23.3
hello
```
#### output
```=
(<type 'int'>, <type 'float'>, <type 'str'>)
(<type 'str'>, <type 'str'>, <type 'str'>)
```
### why not python2 input ??
#### example
```python=
password = "michael"
in_ = input("input password: ")
if in_ == password:
print("Pass")
else:
print("failed")
```
```
input password: "michael"
Pass
```
```
input password: "amy"
failed
```
```
input password: password
Pass
```
## print
### useful reference
https://docs.python.org/3/tutorial/inputoutput.html
### most familiar with c printf
```python=
print('%f %d' %( 3.14 , 3))
```
```
3.140000 3
```
### often use print with "format" function
```python
print("{} {}" .format(3.14, 3))
print("{:f} {:d}" .format(3.14, 3))
print("{1:f} {0:d}" .format(3, 3.14))
print("{1:.4f} {0:5d}" .format(3, 3.14))
```
```
3.14 3
3.140000 3
3.140000 3
3.1400 3
```
### print 不換行
```python=
print("hello world " , end="")
print("test")
```
```
hello world test
```
### print in python2
```python=
print "%d %d" % (1, 2)
print "{} {}" .format(1, 2)
```
```
1 2
1 2
```
# 條件判斷 (注意本章的所有縮排)
## if, if else, if elif else
```python
a = 1
b = 2
if a < b :
print("I")
print("L")
#--------------------
if a > b :
print("B")
else :
print("V")
#--------------------
if a == b :
print("D")
elif a > b :
print("E")
else :
print("P")
print("Y")
```
```
I
L
V
P
Y
```
## python 沒有 switch case ^ ^
## codecademy
https://www.codecademy.com/learn/learn-python
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