Python journey - Data Types

1. Overview

Today to share with you is the data type, data type, degree of importance in Python is like as important than the Chinese pinyin us.

2. Data Types

1. Plastic

Plastic are like mathematics, 2, 3, is represented by int.

a = 1 # 这就是一个整形
print(type(a)) # 可以用type方法来检测数据类型

2. Boolean

A data type that is used to represent the Boolean value of true or false, with bool represented only True and False

3. String

Like a string of Chinese characters, as expressed by str, the string is to write the code of the most common, python memory string is in accordance with: unicode code storage. For strings are immutable

String There are many ways, this is mainly to say some commonly used methods

Uppercase: upper

v = 'ALEX'
v1 = v.upper()
print(v1)
v2 = v.isupper() # 判断是否全部是大写
print(v2)

Lower case: lower

v = 'alex'
v1 = v.lower()
print(v1)
v2 = v.islower() # 判断是否全部是小写
print(v2)


############ 了解即可
v = 'ß'
# 将字符串变小写（更牛逼）
v1 = v.casefold() # 对于其他国家的语言也可以进行小写转化 
print(v1) # ss
v2 = v.lower()
print(v2)

Determine whether the numbers: isdecimal

v = '1'
# v = '二'
# v = '②'
v1 = v.isdigit()  # '1'-> True; '二'-> False; '②' --> True
v2 = v.isdecimal() # '1'-> True; '二'-> False; '②' --> False
v3 = v.isnumeric() # '1'-> True; '二'-> True; '②' --> True
print(v1,v2,v3)
# 以后推荐用 isdecimal 判断是否是 10进制的数。

# ############## 应用 ##############

v = ['alex','eric','tony']

for i in v:
    print(i)

num = input('请输入序号：')
if num.isdecimal():
    num = int(num)
    print(v[num])
else:
    print('你输入的不是数字')

To Blank + \ t + \ n + a specified string: strip

v1 = "alex "
print(v1.strip())

v2 = "alex\t"
print(v2.strip())

v3 = "alex\n"
print(v3.strip())

v1 = "alexa"
print(v1.strip('al'))

Replace: replace

name = 'alex'
new_name = name.replace('a','T')
print(new_name)

Beginning: starswith

name = 'alex'
new_name = name.startswith('a')
print(new_name)

End: endswith

name = 'alex'
new_name = name.endswith('x')
print(new_name)

encode: the string into binary

name = '你好'
new_name = name.encode('utf-8')
print(new_name)

format: String Format

v1 = "我叫{0}，年龄{1}".format('郭睿杰',23)
print(v1)

join: Join

name = 'alex'
new_name = "|".join(name)
print(new_name)

split: split

name = 'alex'
new_name = name.split("l")
print(new_name)

Other [optional]

4. List

Like a list of containers, which it can store many types of data, with list to represent. And inside the content can be modified

A list of commonly used methods:

Add: append
```
v1 = [1,2,3,4]
v1.append(5)
print(v1)
```
Insert: insert
```
v1 = [1,2,3,4]
v1.insert(0,1)
print(v1)
```

Delete: remove

v1 = [1,2,3,4]
v2 = (5,6,7,8)
v1.remove(1)
print(v1)

Delete: pop

v1 = [1,2,3,4]
v2 = (5,6,7,8)
v1.pop(1)
print(v1)

Delete: clear

v1 = [1,2,3,4]
v2 = (5,6,7,8)
v1.clear()
print(v1)

Adding another list (tuple) to the first element in the list: extend
```
v1 = [1,2,3,4]
v2 = (5,6,7,8)
v1.extend(v2)
print(v1)
```

Reverse: reverse

v1 = [1,2,3,4]
v2 = (5,6,7,8)
v1.reverse()
print(v1)

Sort: sort

v1 = [1,2,3,4]
v2 = (5,6,7,8)
v1.sort(reverse=False)
print(v1)

5-tuple

Is also a container, the content inside can not be amended. Expressed with tuple
General Procedure tuple, due to its nature can not be modified, it has some basic method is a method:
1. Take length: len
2. index
3. slice
4. Steps

6. Dictionary

The same type of container is a dictionary data type, represented by dict, it lists and tuples difference is that it has its own key-value pairs, i.e. keys and values, the same dictionary key is not allowed to modify , but the value can be modified

Dictionary of commonly used methods:

Take all of the keys: keys

v1 = {'k1':1,'k2':2}
for i in v1.keys():
    print(i)

Take all values: values

v1 = {'k1':1,'k2':2}
for i in v1.values():
    print(i)

Take all of the key-value pairs: items

v1 = {'k1':1,'k2':2}
for a,b in v1.items():
    print(a,b)

Value: get

v1 = {'k1':1,'k2':2}
x = v1.get('k1')
print(x)

Delete: pop

v1 = {'k1':1,'k2':2}
v1.pop('k1')
print(v1)

Update: update

v1 = {'k1':1,'k2':2}
v1.update({'k3':3})
print(v1)

Ordered dictionary

from collections import OrderedDict

info = OrderedDict()
info['k1'] = 123
info['k2'] = 456

print(info.keys())
print(info.values())
print(info.items())

7. collection

As a set of data type container type, which is characterized not repeated. Is represented by set

Common methods for the collection

Add: add
```
v1 = {1,2,3,4}
v1.add(666)
print(v1)
```
Delete: discard
```
v1 = {1,2,3,4}
v1.discard(1)
print(v1)
```

Bulk add: update

v1 = {1,2,3,4}
v1.update({7},{8},{9})
print(v1)

Take the intersection: intersection

v1 = {1,2,3,4}
v2 = {3,4,5,6}
x = v1.intersection(v2)
print(x)

Take the union: union

v1 = {1,2,3,4}
v2 = {3,4,5,6}
x = v1.union(v2)
print(x)

Set taking the difference: difference

v1 = {1,2,3,4}
v2 = {3,4,5,6}
x = v1.difference(v2)
print(x)

8.None

This data type is like surface means, means is empty.

9. summary

Today to share some of our commonly used data types, as well as some of their common method, welcome to discuss!