python-賀威棟-2021.01.20

'''遞歸函數(shù)'''

# n!=1*2*3*4*...*n

def factorail(n):

    s = 1

    for i in range(1,n+1):

        s *= i

    return s

print(factorail(5))

'''

n! = (n-1)!*n

(n-1)! = (n-2)!*(n-2)

2! = (2-1)!*2

1! = 1

'''

# 遞歸函數(shù)

def fact(n):

    if n == 1:    # 遞歸函數(shù)一定要有邊界條件

        return 1

    return fact(n-1)*n   # 遞歸函數(shù)中一定要有對(duì)函數(shù)自己的調(diào)用

print(fact(5))

'''切片'''

names = ['趙夢(mèng)冰','張榮亮','張國(guó)榮','焦新瑞','代金鑫']

'''

names[a:b:c]：表示截取從下標(biāo)a開(kāi)始到下標(biāo)b結(jié)束的所有元素，但不包含b

c表示步長(zhǎng)，默認(rèn)值是1

列表切片后還是列表

元組也可以切片后還是切片

字符串切片后還是字符串

'''

print(names[0:3])

# 如果第一個(gè)索引是0，可以省略不寫(xiě)

print(names[:3])

# 如果一直截取到末尾，第二個(gè)索引可以省略不寫(xiě)

print(names[3:])

# 復(fù)制列表

l = names[:]

print(l)

# 切片時(shí)可以指定步長(zhǎng)，默認(rèn)值是1

print(names[::2])

# 元組切片后還是切片

name = ('趙夢(mèng)冰','張榮亮','張國(guó)榮','焦新瑞','代金鑫')

print(name[0:3])

# 字符串切片后還是字符串

s = 'abcdef'

print(s[:])

'''迭代'''

names = ['趙夢(mèng)冰','張榮亮','張國(guó)榮','焦新瑞','代金鑫']

# 循環(huán)，遍歷，迭代 Iteration

# names：可迭代對(duì)象    列表，元組，字典，字符串

for name in names:

    print(name)

# 遍歷key

name_scores = {'趙夢(mèng)冰':88,'張榮亮':99,'侯富軍':77,'王顏麗':89,'焦新瑞':93,'張國(guó)榮':98}

for key in name_scores:

    print(key,name_scores[key])

# 遍歷value

for value in name_scores.values():

    print(value)

# 同時(shí)遍歷key和value

for key,value in name_scores.items():

    print(key,value)

# 遍歷字符串

for char in 'abcdef':

    print(char)

'''判斷對(duì)象是否可迭代'''

from collections.abc import Iterable

# isinstance(obj,type)判斷對(duì)象obj是否是type類(lèi)型，是則返回True，否則返回False

print(isinstance(1,int))

print(isinstance('1',str))

print(isinstance('1',int))

print(isinstance(names,Iterable))

# 循環(huán)遍歷

for i,char in enumerate('abcdef'):

    print(i,char)

'''

列表生成式

'''

nums = list(range(10))

print(nums)

# [1*1,2*2,3*3,...9*9]

# 方法一

nums = []

for x in range(1,10):

    nums.append(x*x)

print(nums)

# 方法二  列表生成式  # ☆☆☆

m = [x*x for x in range(1,10)]

print(m)

# 用列表生成：[1,1/2,1/3，

n = [1/x for x in range(1,10)]

print(n)

# 列表生成式中添加條件判斷

o = [x*x for x in range(1,10) if x%2==0]

print(o)

# 列表生成式中使用多重循環(huán)

p = [x+y for x in 'ABC' for y in 'XYZ']

print(p)

# 用列表生成式生成元組

q = tuple([x*x for x in range(1,10)])

print(q)