数据团Python_6. 条件判断及循环语句

6. 条件判断及循环语句

6.1 什么是语句

>>> #赋值语句
>>> x = 1
>>> x = [1, 3, 5]
>>> x = {'a':'b'}
>>> 
>>> #运行函数/方法
>>> print('a')
a
>>> str(123)
'123'
>>> list('abc')
['a', 'b', 'c']
>>> dict(m = 'a', n = 'b')
{'n': 'b', 'm': 'a'}
>>> list(range(10)) #函数运行
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> x = list(range(10))
>>> x
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> x.copy() #方法
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> x.remove(1)
>>> x
[0, 2, 3, 4, 5, 6, 7, 8, 9]
>>> 
>>> #if语句
>>> x = 10
>>> if x > 5 :
    print('大')

    
大
>>> 
>>> #for循环（迭代）
>>> m = list(range(20))
>>> m
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19]
>>> for i in m:
    print(i)

    
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
>>> 
>>> n = tuple(range(20))
>>> n
(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
>>> for i in n :
    print(i)

    
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
>>> b = {'a':1, 'b':2}
>>> for i in b:
    print(i)

    
a
b
>>> for (k,v) in b.items() :
    print('{}-{}'.format(k,v))

    
a-1
b-2
>>> 
>>> #while语句（循环）
>>> x = 1
>>> while x < 10:
    print(x)
    x = x + 1

    
1
2
3
4
5
6
7
8
9
>>> 
>>> #def函数
>>> def f():
    print('hello world')

    
>>> f()
hello world
>>> 
>>> #模块语句import
>>> 
>>> #类class
>>> 
>>> x = 1
>>> y = 2
>>> z = 3
>>> print(x + y + z)
6

6.2 if语句

x = 12
if x <18 :
    print('18岁以下不宜观看')

#具有相同缩进的代码将被视为代码块

y = 20
if y >18 :
    print('hehe')

#input()函数，该函数的输入为字符串
m = input('m=')
print(m)

score = input('score=')
score1 = float(score)
if score1>=60 :
    print('及格')
else: #注意缩进
    print('重修')
    
score = input('score=')
score1 = float(score)
if score1 >= 85 :
    print('A')
elif score1 >= 60: #注意elif
    print('B')
else:
    print('C')

#作业
st = input('请输入语句：')
if eval(st) == True: #eval()执行括号内语句
    print('真')
else:
    print('假')

n = int(input('请猜数字：'))
m = 50
if n == m :
    print('Good!')
elif n > m :
    print('大了')
else:
    print('小了')

6.3 for 循环

#前边的丢了
#前边的丢了
#前边的丢了
k = ['a', 'b', 'c']
v = [1, 2, 3]
#[['a':1], ['b':2], ['c':3]]
m = []
for i in range(len(k)):
    m.append([k[i],v[i]])
m2 = dict(m)
print(m)

#阶层运算
n = int(input('阶层运算n = '))
m = 1

for i in range(1, n+1) :
    m = m * i
print(m)

6.4 while循环

while True : #死循环
    print('stop , Hit the friendly army !')
#if while 对比
n = int(input('n = '))

if n < 18 :
    print('Too tender')

while n <18 :
    print('too tender')
    break #停止运行

#求和0-100
x = 0
s = 0

while x < 100 :
     s = s + x
     x = x +1

print(s)

#continue继续下一循环
lst = list(range(1,6))
s = 0

for i in lst :
    if i%2 != 0 : #验证为是否为奇数
        s = s + i
    else :
        continue

print(s)

6.5 多重循环

#for while 相互嵌套, if辅助判断
#乘法口诀表
for i in range(1, 10) :
    for j in range(1, 10) :
        m = i * j
        print(str(i) + '*' + str(j) + '=' + str(m))
    print('\n')

st1 = 'abc'
st2 = '123'

n = len(st1)
m = []

for i in range(n) :
    for j in range(n) :
        m.append(st1[i] + st2[j])

print(m)

for i in range(n) :
    m.append(st1[i] + st2[i])

print(m)

st = input('随机输入一行字符串：')
x = input('输入想查找的字母x = ')

m = []
l = len(st)

for i in range(l) :
    al = st[i]
    if al == x :
        m.append(i)
    else:continue

print(m)

print('输入a或者b')

x = input('a燕麦面板，b普通面包 : ')
y = input('a要番茄酱，b不要番茄酱:')
z = input('a打包，b不打包 : ')

if x == 'a'  :
    if y == 'a' :
        if z == 'a' :
            print('燕麦面包+番茄酱+打包')
        else :
            print('燕麦面包+番茄酱+不打包')
        

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