Python基础

for i in range(1,10,2): #2.步长
	print(i)
	print(i**2) #平方

import numpy as np
for k in np.arange(0,1,0.1):
    print(k)

aList = [1,5,6,8,12,54,66]
for item in aList:
    print(item)
print('continue')

t = [1,2,3,4,5,6,7,8,9,10]
for i in range(4,8):
    print(t[i] ** 2)
print('---------------')
for k in t[4:8]:
    print(t[k]*2)

d = { 'Name':'lili', 'Age': 18}
for i,j in d.items():
    print(i,j)
print('---------------')
# 输出key
for i in d.keys():
    print(i)
print('---------------')
# 输出value
for i in d.values():
    print(i)

x = 8
y = 3
z = 8

if x == y:
    print('x is equal to y')
elif x > y:
    print('x is bigger than y')
else:
    print('x is not equal to y')

for i in range(1,10):
    if i % 2 == 0:
        print("%d is even" %i)
    elif i % 3 == 0:
        print("%d is multiple of 3" %i)
    else:
        print("%d is odd" % i)

total = 0
while total < 10:
    total += 1
print("sum = %d" %total)

a = 1
while a < 6:
    if a < 3:
        print(a)
    elif(a == 3):
        print('a==3')
    else:
        print('python')
    a += 1

a = 1
while a:
    print(a)
    a += 1
    if a == 5:
        break
a

a = 1
while a<7:
    a+=1
    if a == 3:
        continue
    print(a)

m = [i ** 2 for i in range(5)]
m

m = []
for i in range(5):
    m.append(i**2)
m

a = ['a','b','c']
b = [1,2,3]

c = zip(a,b)
print(type(c))
print(list(zip(a,b)))
print(dict(zip(a,b)))

def f(x):
    return x * x
f(66)

m = [1,2,3,4,5]
results = [f(x) for x in m]
print(results)

import math

for i in [1,2,3,-4,-5,6,7,8,'python3']:
    try:
        print("%d 的开根号值是 %f" %(i, math.sqrt(i)))
    except ValueError:
        print("无法计算 %d的开根号值" %i)
    except TypeError:
        print("输入 %s的类型不对，它不是一个数字" %i)
    else:
        print("计算成功")
    finally:
        print("进行下一次计算")

def prime_choice(a): 
    pass              #啥也不干

prime_choice('a')

def prime_choice(a):
    if type(a) != int:
        raise TypeError("输入类型错误")
    print("输入类型正确")

prime_choice(10)
prime_choice("python3")

def prime_choice(a):
    if isinstance(a,int):
        print("输入类型正确")
    else:
        raise TypeError("输入类型错误")

#prime_choice('python')
prime_choice(10)

def prime_choice(a):
    if isinstance(a,int) == False:
        raise TypeError("输入类型错误")
    for i in range(2,a):
        if a % i == 0:
            print("它不是质数，它可以被%d整除" %i)
        if i == a - 1:
            print("%d是质数" %a)


prime_choice(7)

def MultipleArg(*args):  # 不定长参数
    for i in args:
        print(i)

MultipleArg(2,4,9)

square = lambda x, y : x ** y
square(3,3)

#map函数  map(function, sequence):对sequence中的item依次执行function(item),将执行结果组成一个List返回

def even2(x):
    return x%2 == 0

map(even2,range(10)) #python3 -map里面返回的是一个map对象

list(map(even2,range(10)))

for i in map(even2,range(10)):
    print(i)

#lambda表达式
for i in map(lambda x: x**2, range(10)):
    print(i)

#通过map实现对字符串格式化
l = ['java', 'python','C#']
a = list(map(lambda x: x.upper(), l))
print(a)

l = [2,-1,3,4,8,-9]
a = list(map(lambda x: abs(x), l))
print(a)

True
False
True
False
True
False
True
False
True
False
0
1
4
9
16
25
36
49
64
81
['JAVA', 'PYTHON', 'C#']
[2, 1, 3, 4, 8, 9]

#python尽量少用循环
%timeit list(map(even2,range(10000000)))
%timeit [even2(x) for x in range(10000000)]

#Reduce函数
#reduce(function,sequence,starting_value):对sequence中的item顺序迭代调用function，如果有starting_value，还可以作为初始
#值调用，例如可以对list求和

from functools import reduce

def add(x,y):
    return x + y

reduce(add,range(1,11))

reduce(add,range(1,11),20) # 20+1+2+3+4+5+6+7+8+9+10 可以有初始值，20作为函数计算的初始值

75

#filter函数
#filter(functioin,sequence):对sequence中的item依次执行function(item),
#将执行结果为True的item组成一个List/String/Tuple(取决于)

list(filter(lambda x: x<0, range(-5,5))) # python3 会返回一个可以迭代的filter对象，用list可以返回具体的值

[-5, -4, -3, -2, -1]

#Enumerate函数
exa = ['left','right','up','down']
for i in range(len(exa)):
    print(i,exa[i])

0 left
1 right
2 up
3 down

for i,j in enumerate(exa):
    print(i,j)

0 left
1 right
2 up
3 down