学习Python第三天笔记

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循环控制
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1、从1-10号学生中找到3号学生（假设顺序不固定）
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i = 1
while i <= 10:
# print(i)
if i == 3:
print(i)
# 终止循环
break
i += 1

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1、从1-10号学生中找到除了7号学生的同学
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i = 1
while i <= 10:
if i == 7: # i == 7 死循环(逻辑问题)
i += 1 # 无论是否跳过 i 必须递增1
continue # 跳过本次循环, 继续 下次循环
print(i)
i += 1

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while嵌套—复杂的方式输出星星
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i = 1
while i <= 5:
# 假设 i == 3 5
j = 1
while j <= 1:
print(’*’, end=’’)
j += 1
# 循环结束，需要换行
print()
i += 1

print("*",end="")

print("*",end="")

print("*",end="")

print("*",end="")

print()

print("*") 1

print("**") 2

print("***") 3

print("****") 4

print("*****") 5

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九九乘法表
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print(‘1 * 1 = 1’)
print(‘1 * 2 = 2\t2 * 2 = 4’)
print(‘1 * 3 = 3\t2 * 3 = 6\t3 * 3 = 9’)

print(’*’ * 99)

99乘法表

i = 1 # i代表乘数
while i <= 9:
# 循环获取被乘数
j = 1 # 被乘数
while j <= i:
print(’%dx%d=%2d’ % (j, i, j * i), end=’\t’)
j += 1
# 换行
print()
i += 1

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while_else语句了解
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循环输出1-10，如果循环结束提示一下

i = 1
while i <= 10:
print(i)
if i == 7:
break
i += 1
else:
print(‘循环结束了，提示一下’)
print(‘end…’)

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列表概念
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定义列表

names = [‘张飞’, ‘刘备’, ‘关羽’]

names = list([‘张飞’,‘刘备’,‘关羽’])

print(names)

取元素

print(names[1])

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列表
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score = [90, 80, 90, 99, 100] # 索引=长度-1
print(score[1:4])
print(score[-1:-3:-1]) # [100, 99]
print(score[::-1]) # 逆序排列列表

排序

score.sort(reverse=True) #没有返回值

print(score)

score.reverse() # 修改了原序列，将其逆序
print(score)

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遍历列表
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score = [80, 77, 99, 100, 66]
i = 0
while i < len(score):
print(score[i])
i += 1
print(’+’ * 100)

倒着取值

i = 4
while i >= 0:
print(score[i])
i -= 1

print(score[4])

print(score[3])

print(score[2])

print(score[1])

print(score[0])

print(score[0])

print(score[1])

print(score[2])

print(score[3])

print(score[4])

print(’=’ * 100)

for … in … 遍历

for i in score:
print(i)

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列表嵌套
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列表嵌套

students = [
[‘刘备’, ‘关羽’, ‘张飞’],
[‘貂蝉’, ‘大乔’, ‘小乔’]
]

遍历

for i in students:
for j in i:
print(j)

print(students[1000]) IndexError: list index out of range (索引 index)

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元组了解
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names = (‘张飞’, ‘关羽’, ‘曹操’)
print(names)
print(type(names))
print(names[0:2])

names[0] = ‘刘备’ TypeError:‘tuple’ object does not support item assignment

info = (‘张飞’, 24, ‘男’)

print(info)

使用三个变量存储数据, 拆分

name = info[0]

age = info[1]

sex = info[2]

name, age, sex = info
print(name, age, sex)

定义单元素元组

names = (‘刘备’,)
print(names)
print(type(names))
names2 = tuple([‘张飞’])
print(names2)
print(type(names2))

列表和元组直接的相互转换

names = (‘刘备’, ‘关羽’, ‘张飞’, ‘貂蝉’, ‘小乔’)
list_names = list(names) # 转换成列表
print(list_names)
tuple_names = tuple(list_names) # 转换成立元组
print(tuple_names)