> For the complete documentation index, see [llms.txt](https://jen-hsuan-hsieh.gitbook.io/python/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://jen-hsuan-hsieh.gitbook.io/python/chapter-2courses/21python-for-data-science-and-machine-learning-bootcamp/212python-crash-course.md).

# 2.1.2.Python crash course

## String

* print and format的方式

```
print('My number is: {one}, and my name is: {two}, more {one}'.format(one=num,two=name))
```

* concate

## List, Tuple, Dictionary, Set

* List
  * 可讀可寫

    ```
    l = [1,2,3]
    item = l.pop()
    l.append('new')
    'x' in ['x', 'y', 'z'] //return True

    x = [(1, 2), (3, 4), (5, 6)]
    for a, b in x:
      print(a)
      print(b)
    ```
* Tuple
  * 只有初始化時可賦值

    ```
    t = (1,2,3)
    ```
* Dictionary
  * key可以是string或是number

    ```
    d = {'key1':'item1','key2':'item2'}
    d.keys()
    d.items()
    d.values()
    ```
* Set
  * 只會儲存唯一值

    ```
    In : {1,2,3,1,2,1,2,3,3,3,3,2,2,2,1,1,2}
    Out: {1, 2, 3}
    ```

## Function

* 定義function

```
def my_func(param1='default'):
    """
    Docstring goes here.
    """
    print(param1)
```

## Map

* 根據提供的函數對指定序列做映射

```
def times2(var):
    return var*2

seq = [1,2,3,4,5]
map(times2,seq)
```

## lambda expressions

```
t = lambda var: var*2
t(2)
```

## filter

* 以傳入的boolean function作為條件函式, iterate所有的sequence的元素並收集 function(元素) 為True的元素到一個List

```
seq = [1,2,3,4,5]
list(map(lambda var: var*2,seq))
```