【Kaggle Learn】Python 1-4

绝地灬酷狼 2022-03-17 06:20 165阅读 0赞

> 【Kaggle Learn】Python [https://www.kaggle.com/learn/python][https_www.kaggle.com_learn_python]

# 一. Hello, Python #

> A quick introduction to Python syntax, variable assignment, and numbers

spam_amount = 0
    print(spam_amount)
    
    # Ordering Spam, egg, Spam, Spam, bacon and Spam (4 more servings of Spam)
    spam_amount = spam_amount + 4
    
    if spam_amount > 0:
        print("But I don't want ANY spam!")
    
    viking_song = "Spam " * spam_amount
    print(viking_song)
    
    """ The result is: 0 But I don't want ANY spam! Spam Spam Spam Spam """

①无分号 ;

②printf（）

③if a>0 ：  
printf()  
if语句用冒号 ：

④注释单行用\#，注释多好用三个 ’ 单引号或三个 " 双引号

⑤注意要用英文字符

⑥变量无需定义类型，字符串可直接相乘，如"Spam"\*4  
另外也可以用type（）得出当前变量的类型

①c语言以及matlab的基本操作可以用在python上，还有a//b,a\*\*b,-a  
a//b : a/b去小数  
a \*\* b : a^b  
\-a : a的相反数

②printf（）用法

print("Height in meters =", total_height_meters, "?")
    #Height in meters = 26.9 ?

③其他函数  
min()  
max()  
abs()

float()  
int()

# 二. Exercise: Syntax, Variables, and Numbers #

略

# 三. Functions and Getting Help #

> Calling functions and defining our own, and using Python’s builtin documentation

round() 浮点数四舍五入，可多小数位

定义函数

def least_difference(a, b, c):
        diff1 = abs(a - b)
        diff2 = abs(b - c)
        diff3 = abs(a - c)
        return min(diff1, diff2, diff3)

①def语句也要用冒号 ：

②输入多行代码  
(1)命令行下  
在 ： 后面按回车，然 后按Tab，打代码，按回车，以此类推，最后按两次回车。  
![在这里插入图片描述][20190222165654867.png]  
(2)记事本转.py后, 打开python shell, 写代码, 按F5或Run-Run module  
此时的def也要有一个Tab缩进(其实空格也行 不好看…)  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjQ3OTA5Mg_size_16_color_FFFFFF_t_70]

③docstrings 其实就是注释  
要善于写注释

④当def里面没有return 此时用print(def(1,2,3)) 输出None

⑤输出help（print）可知print原型

print(value, ..., sep=' ', end='\n', file=sys.stdout, flush=False)
    不改即为默认值
    
    如:
    print(1, 2, 3)
    1 2 3
    
    print(1, 2, 3, sep=' < ')
    1 < 2 < 3
    
    也可这样用print
    
    print(
        call(mult_by_five, 1),
        squared_call(mult_by_five, 1), 
        sep='\n', # '\n' is the newline character - it starts a new line
    )

调用函数

def greet(who="Colin"):
        print("Hello,", who)
        
    greet()
    greet(who="Kaggle")
    # (In this case, we don't need to specify the name of the argument, because it's unambiguous.)
    greet("world")
    
    """ The result is: Hello, Colin Hello, Kaggle Hello, world """

调用方式很多

(1)定义函数时可以用其他函数

def mult_by_five(x):
        return 5 * x
    
    #相当于调用一次mult_by_five(x)
    def call(fn, arg):
        """Call fn on arg"""
        return fn(arg)
    
    #相当于调用一次mult_by_five( mult_by_five(x) )
    def squared_call(fn, arg):
        """Call fn on the result of calling fn on arg"""
        return fn(fn(arg))
    
    print(
        call(mult_by_five, 1),
        squared_call(mult_by_five, 1), 
        sep='\n', # '\n' is the newline character - it starts a new line
    )
    """ The result is: 5 25 """

(2)调用函数(如max函数)时用其他函数

def mod_5(x):
        """Return the remainder of x after dividing by 5"""
        return x % 5
    
    print(
        'Which number is biggest?',
        max(100, 51, 14),
        'Which number is the biggest modulo 5?',	
        #通过改变key,使max函数先对数进行mod5,操作再取最大值
        max(100, 51, 14, key=mod_5),
        sep='\n',
    )
    
    #max原型为 max(arg1, arg2, *args, *[, key=func]) -> value
    
    """ The result is: Which number is biggest? 100 Which number is the biggest modulo 5? 14 """

# 四. Exercise: Functions and Getting Help #

round原型round(number, ndigits=None)  
①当ndigits为正数, 对小数点后n位四舍五入  
如

>>> round(1.0016,3)
    1.002
    >>> round(1.0014,3)
    1.001

①当ndigits为负数, 对小数点前n位四舍五入  
如

>>> round(2166086,-3)
    2166000
    >>> round(2166086,-2)
    2166100
    >>>

**Tip**: In the kernel editor, you can highlight several lines and press `ctrl`\+`/` to toggle commenting.

time函数用法【略】  
①  
The time function returns the number of seconds that have passed since the Epoch (aka \[Unix time\]).  
Epoch:January 1, 1970, 00:00:00 (UTC)

from time import time
    t = time()
    print(t, "seconds since the Epoch")
    
    #1550835855.8225462 seconds since the Epoch
    #1550835865.3415313 seconds since the Epoch

②停几秒再输出,用sleep()

from time import sleep
    duration = 5
    print("Getting sleepy. See you in", duration, "seconds")
    sleep(duration)
    print("I'm back. What did I miss?")
    
    #Getting sleepy. See you in 5 seconds
    #这里经过了5秒
    #I'm back. What did I miss?

③计算调用某个函数用了多久,用time()

def time_call(fn, arg):
        """Return the amount of time the given function takes (in seconds) when called with the given argument. """
        pass
    	t0 = time()
    	fn(arg)
    	t1 = time()
    	elapsed = t1 - t0
    	return elapsed
    """ def time_call(fn, arg1,arg2): pass t0 = time() fn(arg1,arg2) t1 = time() elapsed = t1 - t0 return elapsed print(time_call(max,1,2)) 9.5367431640625e-07 """

[https_www.kaggle.com_learn_python]: https://www.kaggle.com/learn/python
[20190222165654867.png]: /images/20220317/7a1eef921694411490d08a2ee12ef0d5.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjQ3OTA5Mg_size_16_color_FFFFFF_t_70]: /images/20220317/c53d73a394b44ae7b4a3c11406012cd1.png