python杂学

# 交换变量
a = 2
b = 4
a,b = b,a
print(a,b)

4 2

# 转义
str1 = r"我在\n华为"
str2 = "我在\n华为"

print(str1)

print()

print(str2)

我在\n华为

我在
华为

# 除法
print(10 / 3)
print(10 / 3.0)
print(10 // 3)

3.3333333333333335
3.3333333333333335
3

# 二维列表
list1 = []
for i in range(2):
    list1.append([])
    for j in range(3,10,2):
        list1[i].append(j)
print(list1)
print(list1[1][1])

[[3, 5, 7, 9], [3, 5, 7, 9]]
5

# 连接字符串：
str1 = "we are a warm"
str2 = "family"
print(str1 + " " + str2)

print()

str3 = [str1,str2]
print(' '.join(str3))

we are a warm family

we are a warm family

help(str.split)

Help on method_descriptor:

split(self, /, sep=None, maxsplit=-1)
    Return a list of the words in the string, using sep as the delimiter string.
    
    sep
      The delimiter according which to split the string.
      None (the default value) means split according to any whitespace,
      and discard empty strings from the result.
    maxsplit
      Maximum number of splits to do.
      -1 (the default value) means no limit.

# 拆分字符串到一个列表
str1.split(sep = " ")

['we', 'are', 'a', 'warm']

string1 = "believe,lie,lie"
string1.count("lie")

3

string1.find("lie")

2

names = ["磊","亚","涛","虎","光","敏","海","丹"]

操作列表

for name in names:
    print(name)

磊
亚
涛
虎
光
敏
海
丹

help(print)

Help on built-in function print in module builtins:

print(...)
    print(value, ..., sep=' ', end='\n', file=sys.stdout, flush=False)
    
    Prints the values to a stream, or to sys.stdout by default.
    Optional keyword arguments:
    file:  a file-like object (stream); defaults to the current sys.stdout.
    sep:   string inserted between values, default a space.
    end:   string appended after the last value, default a newline.
    flush: whether to forcibly flush the stream.

for name in names:
    print(name, end = " ")

磊 亚 涛 虎 光 敏 海 丹 

names.index("丹")

7

for index,name in enumerate(names):
    print(index,name)

0 磊
1 亚
2 涛
3 虎
4 光
5 敏
6 海
7 丹

for i in range(5):
    print(i,end = ' ')
print()
for j in range(1,4):
    print(j,end = ' ')
print()
for m in range(1,10,2):
    print(m,end = ' ')

0 1 2 3 4 
1 2 3 
1 3 5 7 9 

list2 = [x for x in range(9)]
list2

[0, 1, 2, 3, 4, 5, 6, 7, 8]

max(list2)

8

min(list2)

0

list2.count(8)

1

from collections import Counter
dict(Counter(list2))

{0: 1, 1: 1, 2: 1, 3: 1, 4: 1, 5: 1, 6: 1, 7: 1, 8: 1}

list2[1:3]  # 左闭右开

[1, 2]

list2[:]

[0, 1, 2, 3, 4, 5, 6, 7, 8]

list2[::2]

[0, 2, 4, 6, 8]

list2[-2:]

[7, 8]

list3 = [range(2,8)]
list4 = [range(9,10)]
if list3 == list4:
    print("yes")
else:
    print("no")
if 3 not in list3 and 7 not in list3:
    print("not in")
else:
    print("in")
# if
# elif
# else

no
not in

字典

AMP = {"虎":"男","磊":"男","丹":"女","亚":"女"}

AMP["虎"]

'男'

AMP["敏"] = "女"
AMP

{'丹': '女', '亚': '女', '敏': '女', '磊': '男', '虎': '男'}

AMP["亚"] = "男"
AMP

{'丹': '女', '亚': '男', '敏': '女', '磊': '男', '虎': '男'}

AMP_name = ["虎","磊","丹","亚"]
AMP_sex = ["男","男","女","女"]
dict1 = dict(zip(AMP_name,AMP_sex))
dict1

{'丹': '女', '亚': '女', '磊': '男', '虎': '男'}

dict1.get("丹",-1)

'女'

dict1.get("飞","AMP无此人")

'AMP无此人'

for key,value in AMP.items():
    print(key,value)

虎 男
磊 男
丹 女
亚 男
敏 女

for key in AMP.keys():   # 默认
    print(key)

虎
磊
丹
亚
敏

for value in AMP.values():
    print(value)

男
男
女
男
女

集合

import warnings
warnings.filterwarnings("ignore")

list5 = [1,2,4,6,8,2,6]
print(set(list5))

{1, 2, 4, 6, 8}

set1 = {1,4,7,9}
type(set1)

set

set2 = set()    # 无序
set2.add(5)
set2

{5}

set3 = {"c","c++","python","R"}
set4 = {"java","python"}
print(set3 | set4) # 并集
print(set3 & set4) # 交集
print(set3 - set4) # 差集，前者有后者没有

{'R', 'c++', 'java', 'python', 'c'}
{'python'}
{'R', 'c++', 'c'}

while

str2 = input("请输入：")
str2

请输入：6





'6'

str2 = int(input("请输入："))
str2

请输入：6





6

i = 6
while i > 0:
    if i > 3:
        i -= 1
        continue
    print("end")
    i -= 1

end
end
end

list6 = []
text = input("请输入性别：")
while text != "q":
    list6.append(text)
    text = input("请输入性别：")
list6

请输入性别：女
请输入性别：男
请输入性别：q





['女', '男']