[重学Python] Day1 变量+分支+循环

import this 

Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.
Special cases aren't special enough to break the rules.
Although practicality beats purity.
Errors should never pass silently.
Unless explicitly silenced.
In the face of ambiguity, refuse the temptation to guess.
There should be one-- and preferably only one --obvious way to do it.
Although that way may not be obvious at first unless you're Dutch.
Now is better than never.
Although never is often better than *right* now.
If the implementation is hard to explain, it's a bad idea.
If the implementation is easy to explain, it may be a good idea.
Namespaces are one honking great idea -- let's do more of those!

优美比丑陋好
清晰比晦涩好
简单比复杂好
复杂比错综复杂好
扁平比嵌套好
稀疏比密集好
可读性很重要
特殊情况也不应该违反这些规则
但现实往往并不那么完美
异常不应该被静默处理
除非你希望如此
遇到模棱两可的地方，不要胡乱猜测
肯定有一种通常也是唯一一种最佳的解决方案
虽然这种方案并不是显而易见的，因为你不是那个荷兰人[这里指的是Python之父Guido]
现在开始做比不做好
不做比盲目去做好
如果一个实现方案难于理解，它就不是一个好的方案
如果一个实现方案易于理解，它很有可能是一个好的方案
命名空间非常有用，我们应当多加利用

a = 666
b = 888
print(a + b)
print(a - b)
print(a * b)
print(a / b)
​
输出结果
1554
-222
591408
0.75

a = 1
b = 0.01
c = True
d = '你好'
e = 1 + 5j
print(type(a))
print(type(b))
print(type(c))
print(type(d))
print(type(e))
​
输出结果
<class 'int'>
<class 'float'>
<class 'bool'>
<class 'str'>
<class 'complex'>

a = float(input('a = '))
b = int(input('b = '))
print('%d + %d = %d' % (a, b, a + b))
print('%d - %d = %d' % (a, b, a - b))
print('%d * %d = %d' % (a, b, a * b))
print('%d / %d = %f' % (a, b, a / b))
print('%d // %d = %d' % (a, b, a // b))
print('%d %% %d = %d' % (a, b, a % b))
print('%d ** %d = %d' % (a, b, a ** b))
​
输入内容
a = 4.0 b = 6
输出内容
4 + 6 = 10
4 - 6 = -2
4 * 6 = 24
4 / 6 = 0.666667
4 // 6 = 0
4 % 6 = 4
4 ** 6 = 4096

经典题目：输入年份判断闰年
year = int(input('请输入年份'))
leap_year = year % 4 == 0 && year % 100 != 0 || year % 400 == 0
print(leap_year)
​
输入：2000
结果：True

题目：百分制成绩转换为等级制成绩
如果输入的成绩在90分以上（含90分）输出A；80分-90分（不含90分）输出B；70分-80分（不含80分）输出C；60分-70分（不含70分）输出D；60分以下输出E。
​
score = float(input('请输入成绩'))
if score >= 90:
    print('Your Grage is A Level')
elif score >= 80 and score < 90:
    print('Your Grage is B Level')
elif score >= 70 and score < 80:
    print('Your Grage is C Level')
elif score >= 60 and score < 70:
    print('Your Grage is D Level')
else:
    print('Your Grage is E Level')

题目：分段函数求职
		x - 5	(x > 1)
f(x) =	x + 2	(-1 <= x <= 1)
		x + 3	(x < -1)

x = float(input('Please enter the value of X'))
if x > 1:
    result = x - 5
else:
    if x >= -1:
        result = x + 2
    else:
        result = x + 3
print('The result is %f' % result)

range()函数
- `range(101)`：可以用来产生0到100范围的整数，需要注意的是取不到101。
- `range(1, 101)`：可以用来产生1到100范围的整数，相当于前面是闭区间后面是开区间。
- `range(1, 101, 2)`：可以用来产生1到100的奇数，其中2是步长，即每次数值递增的值。
- `range(100, 0, -2)`：可以用来产生100到1的偶数，其中-2是步长，即每次数字递减的值。

题目：实现1到100的偶数求和
sum = 0
for x in range(2,101,2):
    sum += x
print('The sum of even numbers from 1 to 100 is %d' % sum)

题目：实现1到100的偶数求和
sum = 0
sum = 0
for x in range(1,101):
    if x % 2 == 0:                #嵌套了分支结构
        sum += x
print('The sum of even numbers from 1 to 100 is %d' % sum)
相较于第一种方法，第二种的嵌套并不是一种很好的选择

import random

answer = random.randint(1, 100)
counter = 0
while True:
    counter += 1
    number = int(input('Please enter your answer: '))
    if number < answer:
        print('Guess larger')
    elif number > answer:
        print('Guess smaller')
    else:
        print('Congratulations!')
        break
print('You have guessed a total of %d times.' % counter)
if counter > 7:
    print('DO better next time ')

for i in range(1, 10):
    for j in range(1, i + 1):
        print('%d*%d=%d' % (i, j, i * j), end='\t')
    print()

from math import sqrt

num = int(input('请输入一个正整数: '))
end = int(sqrt(num))
is_prime = True
for x in range(2, end + 1):
    if num % x == 0:
        is_prime = False
        break
if is_prime and num != 1:
    print('%d是素数' % num)
else:
    print('%d不是素数' % num)

x = int(input('x = '))
y = int(input('y = '))
# 如果x大于y就交换x和y的值
if x > y:
    # 通过下面的操作将y的值赋给x, 将x的值赋给y
    x, y = y, x
# 从两个数中较小的数开始做递减的循环
for factor in range(x, 0, -1):
    if x % factor == 0 and y % factor == 0:
        print('%d和%d的最大公约数是%d' % (x, y, factor))
        print('%d和%d的最小公倍数是%d' % (x, y, x * y // factor))
        break

*
**
***
****
*****

    *
   **
  ***
 ****
*****

    *
   ***
  *****
 *******
*********

row = int(input('请输入行数: '))
for i in range(row):
    for _ in range(i + 1):
        print('*', end='')
    print()


for i in range(row):
    for j in range(row):
        if j < row - i - 1:
            print(' ', end='')
        else:
            print('*', end='')
    print()

for i in range(row):
    for _ in range(row - i - 1):
        print(' ', end='')
    for _ in range(2 * i + 1):
        print('*', end='')
    print()