python自学入门（打卡五）2022-10-29

函数调用

执行带参函数如果传入的参数的变量，是可变类型（list/dict/set），则内部对这个参数所有的操作结果都会影响外部的参数值。
如果传入的参数变量是不可变类型（string/int/float）,则不影响外部的参数值

#传入的参数变量是不可变类型

# n=1
# def func(a):
#     a=a+1
#     return a
# print(func(n))  #2
# print(n)        #1 外部的n不会变
1
2
3
4
5
6

#传入的参数变量是可变类型

# n=[]
# def fun(a):
#     a.append(1)
#     return a
# print(fun(n)) #[1]
# print(n)      #[1] 外部的n也产生了变化
1
2
3
4
5
6

#可变参数C，入参值3 4 5 都给了C

# def add(a,b,*c):
#     print(type(c))
#     print(c)  # (3, 4, 5)
#
# add(1,2,3,4,5)

#把上面函数中的值求和
# def add(a,b,*C):
#     s1=a+b
#     s2=0
#     for i in C:
#         s2=s2+i
#     sum=s1+s2
#     print("和为：%s" %sum)
# add(1,2,3,4,5)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15

可变参数**C

# def add(a,b,**C):
#     print(type(C)) #
#     print(C)
# add(3,4,C=5,D=1,E=1) #{'C': 5, 'D': 1, 'E': 1}

# 求和
# def add(a,b,**c):
#     s1=a+b
#     s2=0
#     for i in c.values():
#         s2=s2+i
#     print(s1+s2)
# add(1,2,c=3,d=4,e=5) #15
1
2
3
4
5
6
7
8
9
10
11
12
13

#可变参数，两个*（dict类型）要放在一个*（tuple类型）后面。

# def add(a,b,*c,**d):
#     result=a+b
#     s2=s3=0
#     for i in c:
#         s2=s2+i
#     for i in d.values():
#         s3=s3+i
#     return(result+s2+s3)
# print(add(1,2,3,4,c=5,d=6,e=7)) #28
1
2
3
4
5
6
7
8
9

字符串

# s="hello"
# print(isinstance(s,bytes)) #false
#
# s1=s.encode()
# print(isinstance(s1,bytes)) #true
#
# s2=s1.decode()
# print(isinstance(s2,bytes)) #false
1
2
3
4
5
6
7
8

单双引号的应用，转义字符

# a="he's a boy"
# print(a)
#
# b='say "hi!"'
# print(b)
#
# c="say \"hi!\""
# print(c)
#
# d="D:\\\\work\\\\logs"
# print(d) #D:\\work\\logs
#
# e="i am a girl \n he is a boy"
# print(e) #\n换行 \t是八个空格
#
# for i in e:
#      print(i)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17

计算有几个a

# s="aaabbbc"
# count=0
# for i in s:
#     if i=="a":
#         count+=1
# print(count)
1
2
3
4
5
6

去掉a

# s="aaabbbccc"
# print(s.strip("a"))
1
2

去掉空格，字符串拼接思想

# s="a b c d"
# result=""
# for i in s:
#     if i != " ":
#         result=result+i
# print(result)
1
2
3
4
5
6

判断一句话中没有a的单词有几个

#方法一
# s = "i like apple so much ,how about Anna"
# li =s.split()
# # print(li) #['i', 'like', 'apple', 'so', 'much', ',how', 'about', 'Anna']
# count=0
# for i in range(len(li)):
#     for n in li[i]:
#          if n=="a":
#           count+=1
# print(count)

# #方法二
# s = "i like apple so much ,how about Anna"
# li =s.split()
# count=0
# for i in li:
#     if "a"  in i:
#          count+=1
# print(count)

# s=["aaa","bbb","ccccc","abc"]
# count=0
# for i in s:
#     if "a" in i:
#         count+=1
# print(count)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26

把s中偶数位置的字母后加个*

# s="i am a boy!"
# result=""
# for i in range(len(s)):
#     if i%2==0:
#         if (s[i]>="a" and s[i]<="z") or (s[i]>="A" and s[i]<="Z"):
#             result=result+s[i]+'*'
# print(result)
1
2
3
4
5
6
7

模板字符串

#模板字符串 %d只能是数字 %s通用占位符
age=10
sex="girl"
s="i am a %s years old %s" %(age,sex)
print(s) #i am a 10 years old girl
1
2
3
4
5

切片练习

s="abcdefg"
s1=s[0]+s[-1]
print(s1)
s2=s[:2]+s[-2:]
print(s2)
s3=s[0::2]
print(s3)
s4=s[-1::-1]
print(s4)
1
2
3
4
5
6
7
8
9