# Pandas DataFrame to List of Dictionaries:





[https://stackoverflow.com/questions/29815129/pandas-dataframe-to-list-of-dictionaries/29816143#29816143](https://stackoverflow.com/questions/29815129/pandas-dataframe-to-list-of-dictionaries/29816143#29816143)

![在这里插入图片描述](/static/img/images/00849.png)

```python
df.to_dict('records')
```

# Convert list of dictionaries to a pandas DataFrame:

[https://stackoverflow.com/questions/20638006/convert-list-of-dictionaries-to-a-pandas-dataframe](https://stackoverflow.com/questions/20638006/convert-list-of-dictionaries-to-a-pandas-dataframe)

![在这里插入图片描述](/static/img/images/00850.png)

![在这里插入图片描述](/static/img/images/00851.png)


[https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.read_sql.html#pandas.read_sql](https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.read_sql.html#pandas.read_sql)

[https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.read_sql_table.html#pandas.read_sql_table](https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.read_sql_table.html#pandas.read_sql_table)

List of Dictionaries vs Pandas DataFrame 字典列表 vs pandas dataframe

[https://www.runoob.com/python/att-time-strftime.html](https://www.runoob.com/python/att-time-strftime.html)





把datetime对象变成各式各样的字符串~~~~~~~
```python
from datetime import datetime
time = datetime.now()
print(time)
print(time.replace(minute=0, second=0, microsecond=0))
print(time.strftime("%Y-%m-%d nihao %H:%M:%S"))
print(time.strftime("%j"))  # 今天是今年的第几天 001到366
print(time.strftime("%w"))  # 今天是星期几 星期日是第0天 0到6
time1 = datetime(2020, 1, 1)
print(time1.strftime("%j"))  # 今天是今年的第几天 001到366 
```

2020-12-07 14:25:57.538141

2020-12-07 14:00:00

2020-12-07 nihao 14:25:57

342

1

001

把字符串提取解析出datetime对象~~~~~

[https://www.runoob.com/python/att-time-strptime.html](https://www.runoob.com/python/att-time-strptime.html)
```python
import datetime
t=datetime.datetime.strptime('2013-12-30T13:00+08:00', "%Y-%m-%dT%H:%M+08:00")
print(t)
```

python datetime 时间处理

一般的字典





![在这里插入图片描述](/static/img/images/00965.png)


构造：
```python
from collections import defaultdict
dict1 = defaultdict(int)
dict2 = defaultdict(set)
dict3 = defaultdict(str)
dict4 = defaultdict(list)
```

defaultdict接受一个函数作为参数。如果字典里没有找到key，用这个函数构造一个对象返回。

题目：

[https://www.nowcoder.com/practice/03ba8aeeef73400ca7a37a5f3370fe68?tpId=37&tags=&title=&diffculty=0&judgeStatus=0&rp=1](https://www.nowcoder.com/practice/03ba8aeeef73400ca7a37a5f3370fe68?tpId=37&tags=&title=&diffculty=0&judgeStatus=0&rp=1)

python：

```python
from collections import defaultdict
while True:
    try:
        zd=defaultdict(list)
        arr = input().split()
        words = arr[1 :  1+int(arr[0])]
        lookup = arr[-2]
        k = int(arr[-1])
        bro=[]
        #构造字典
        for i in words:
            zd[ "".join(sorted(i))].append(i)
        if "".join(sorted(lookup)) in zd.keys():  #在字典里有
            for i in zd["".join(sorted(lookup))]: #所有相似单词
                if lookup!=i:
                    bro.append(i)#相似不相同的才是兄弟单词
        print(len(bro))
        if bro and k-1<len(bro):
            print(sorted(bro)[k-1])#排序所有兄弟单词 找到第k个
    except:
        break
```

传入

```python
5 abc acb ddd fgh hgf abc 1
```

即zd里用abc acb ddd fgh hgf构造

```python
defaultdict(<class 'list'>, 
{
'abc': ['abc', 'acb'], 
'ddd': ['ddd'], 
'fgh': ['fgh', 'hgf']
})
```

python一个defaultdict的典型用法

阅读：





[https://www.cnblogs.com/downey-blog/p/10483216.html](https://www.cnblogs.com/downey-blog/p/10483216.html)

[https://www.cnblogs.com/downey-blog/p/10482955.html](https://www.cnblogs.com/downey-blog/p/10482955.html)

```python
import copy
cop1 = copy.copy(origin)
cop2 = copy.deepcopy(origin)
```

可变类型：列表，字典

不可变类型：int、float、string、tuple

python里万物皆对象。

 参数传递方式和改变取决于参数是可变类型还是不可变类型。

 copy浅层拷贝，不能拷贝子对象。

 deepcopy浅层拷贝。

 

```python
import copy
lst = [[1,2],3]
lst_cp = copy.copy(lst)
print id(lst)
print id(lst_cp)
print id(lst[0])
print id(lst_cp[0])
```

```python
3072042988
3072043404
3072043020
3072043020
```

python 内存模型 形参 实参 参数传递方式

[https://www.runoob.com/python/python-strings.html](https://www.runoob.com/python/python-strings.html)





## 1 rsplit

rsplit反向分割 从右边分割 1
```python
s = 'das dsa 123'
print(s.rsplit(' ',1))
```

outpuut：`['das dsa', '123']`

## 2 join 将序列中的元素以指定的字符连接生成一个新的字符串

```python
res=[1,2,3]
print("-".join(map(str, res))+"end")
```

## 3 反向遍历字符串
```python
rawstr = input()
res = []
for i in rawstr[::-1]: # 反向遍历
    if int(i) not in res:
        res.append(int(i))
print("".join(map(str,res)))
```

用列表反向

```python
a=list(input())
a.reverse()
print("".join(a))
```

反向遍历
```python
a = input()
res = ""
for i in a[::-1]:
    res += i
print(res)
```

## 4 是否有数字 大小写 长度

```python
while True:
    try:
        line = input()
        a = 0
        b = 0
        c = 0
        d = 0
        flag = True
        for i in line:
            if i.isdigit():
                a = 1
            elif i.islower():
                b = 1
            elif i.isupper():
                c = 1
            else:
                d = 1
        for j in range(len(line) - 3):
            if line.count(line[j:j + 3]) > 1:
                flag = False
        if len(line) > 8 and (a + b + c + d) >= 3 and flag:
            print("OK")
        else:
            print("NG")
    except:
        break
```

## 5 格式化字符串

[https://blog.csdn.net/qq_35085863/article/details/78188286](https://blog.csdn.net/qq_35085863/article/details/78188286)

print(format(1, 'b').rjust(4, '0'))