# 3.2 数据类型

## 列表

列表是我们最以后最常用的数据类型之一，通过列表可以对数据实现最方便的存储、修改等操作。

定义列表

```python
names = ['zhangsan','lisi','wangwu']
```

通过下标访问列表中的元素，下标从0开始计数

```
print(name[0])
```

运行结果为：

zhangsan

**取多个元素**

```python
names[1:4:2]  #取下标1至下标4之间的数字，每隔一个元素，就取一个,包括1，不包括4
```

**追加**

```python
names.append('xiaoliu')
```

**插入**

```
names.insert(1, "aa")
```

运行结果为：

\['zhangsan', 'aa', 'lisi', 'wangwu', 'xiaoliu']

**修改**

```
names[1] = "bb"
```

**删除**

按下标删除

```
del names[1]
```

按指定元素删除

```
names.remove("zhangsan")
```

删除列表中最后一个值

```
names.pop()
```

**扩展**

```
names = ['zhangsan','lisi','wangwu']
ages = ['1','2']
names.extend(ages)
```

输出结果为：

\['zhangsan', 'lisi', 'wangwu', '1', '2']

**拷贝**

```
name2 = names.copy()
```

**统计**

```
num = [1,2,3,4,2,3,4,2]
print(num.count(2))
```

输出结果为：

3

**排序**

```
num = [1,2,3,4,2,3,4,2]
num.sort()
print(num)
```

输出结果为：

\[1, 2, 2, 2, 3, 3, 4, 4]

**翻转**

```
name.reverse()
```

**获取下标**

```
num = [1,2,3,4,2,3,4,2]
print(num.index(3))
```

输出结果为：

2

注意：只返回找到的第一个下标

## 元组

元组其实跟列表差不多，也是存一组数，只不是它一旦创建，便不能再修改，所以又叫只读列表

```
names = ('zhangsan','lisi','wangwu')
print(names, names.count("zhangsan"),names.index("lisi"))
```

输出结果为：

('zhangsan', 'lisi', 'wangwu') 1 1

## 字符串

**特性：不可修改**

**首字母大写**

```python
name = "abc"
print(name.capitalize())
```

输出结果为：

Abc

**大写全部变小写**

```
name = "ABC"
print(name.casefold())
```

输出结果为：

abc

**居中**

```
name = "ABC"
print(name.center(50, "-"))
```

输出结果为：

\-----------------------ABC------------------------

**统计lex出现次数**

```
name = "ABClexjjlllex"
print(name.count('lex'))
```

输出结果为：

2

**将字符串编码成bytes格式**

```
name.encode()
```

**判断字符串是否已Li结尾**

```
name = "ABClexjjlllexLi"
print(name.endswith("Li"))
```

输出结果为：

True

**输出'Wangzhi Clay'， 将\t转换成多长的空格**

```
print("Wangzhi\tClay".expandtabs(20))
```

输出结果为：

Wangzhi Clay

**find 查找A,找到返回其索引， 找不到返回-1**

```
name = "BClexAjjlllex"
print(name.find('A'))
```

输出结果为：

5

**format 格式化输出**

```
msg = "my name is {}, and age is {}"
print(msg.format("clay", 18))
```

输出结果为：

my name is clay, and age is 18

```
msg = "my name is {1}, and age is {0}"
print(msg.format("clay", 18))
```

输出结果为：

my name is 18, and age is clay

```
msg = "my name is {name}, and age is {age}"
print(msg.format(age=18, name="clay"))
```

输出结果为：

my name is clay, and age is 18

**format\_map 格式化输出**

```
msg = "my name is {name}, and age is {age}"
print(msg.format_map({'age':18, 'name':'clay'})
```

输出结果为：

my name is clay, and age is 18

**index 返回索引**

```
name = "BAClexAjjlllex"
print(name.index('A'))
```

输出结果为：

1

**isalnum都是字母和数字**

```
name = "k"
print(name.isalnum())
```

输出结果为：

True

**isdigit 是否为整数**

```
name = "5"
print(name.isdigit())
```

输出结果为：

True

*isnumeric isprintable isspace isupper* ????

**join**

```
print("|".join(['alex', 'jack', 'rain']))
```

输出结果为：

alex|jack|rain

**maketrans 替换**

```
intab = "aeiou"
outab = "12345"
trantab = str.maketrans(intab, outab)
str = "this is string example ... wow!!"
print(str.translate(trantab))
```

输出结果为：

th3s 3s str3ng 2x1mpl2 ... w4w!!

**partition分隔**

```
str = "this is string example ... wow!!"
print(str.partition('is'))
```

输出结果为：

('th', 'is', ' is string example ... wow!!')

**swapcase 大小写互换**

```
msg = "xiaoxieDAXIE"
print(msg.swapcase())
```

输出结果为：

XIAOXIEdaxie

**zfill 用0补齐**

```
msg = "xiaoxieDAXIE"
print(msg.zfill(20))
```

输出结果为：

00000000xiaoxieDAXIE

**ljust 靠左侧补齐**

```
msg = "xiaoxieDAXIE"
print(msg.ljust(20, "-"))
```

输出结果为：

xiaoxieDAXIE--------

**rjust 靠右侧补齐**

```
msg = "xiaoxieDAXIE"
print(msg.rjust(20, "-"))
```

输出结果为：

\--------xiaoxieDAXIE

**isidentifier 检测一段字符串可否被当作标志符，即是否符合变量命名规则**

```
msg = "1_xiaoxieDAXIE"
print(msg.isidentifier())
```

False


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