标签:sum mod driving isod order float swap height 美剧
第1章 Pandas基础
import pandas as pd
import numpy as np
查看Pandas版本
pd.__version__
‘1.0.3‘
一、文件读取与写入
1. 读取
(a)csv格式
df = pd.read_csv(‘data/table.csv‘)
df.head()
|
School |
Class |
ID |
Gender |
Address |
Height |
Weight |
Math |
Physics |
0 |
S_1 |
C_1 |
1101 |
M |
street_1 |
173 |
63 |
34.0 |
A+ |
1 |
S_1 |
C_1 |
1102 |
F |
street_2 |
192 |
73 |
32.5 |
B+ |
2 |
S_1 |
C_1 |
1103 |
M |
street_2 |
186 |
82 |
87.2 |
B+ |
3 |
S_1 |
C_1 |
1104 |
F |
street_2 |
167 |
81 |
80.4 |
B- |
4 |
S_1 |
C_1 |
1105 |
F |
street_4 |
159 |
64 |
84.8 |
B+ |
(b)txt格式
df_txt = pd.read_table(‘data/table.txt‘) #可设置sep分隔符参数
df_txt
|
col1 |
col2 |
col3 |
col4 |
0 |
2 |
a |
1.4 |
apple |
1 |
3 |
b |
3.4 |
banana |
2 |
6 |
c |
2.5 |
orange |
3 |
5 |
d |
3.2 |
lemon |
(c)xls或xlsx格式
#需要安装xlrd包
df_excel = pd.read_excel(‘data/table.xlsx‘)
df_excel.head()
|
School |
Class |
ID |
Gender |
Address |
Height |
Weight |
Math |
Physics |
0 |
S_1 |
C_1 |
1101 |
M |
street_1 |
173 |
63 |
34.0 |
A+ |
1 |
S_1 |
C_1 |
1102 |
F |
street_2 |
192 |
73 |
32.5 |
B+ |
2 |
S_1 |
C_1 |
1103 |
M |
street_2 |
186 |
82 |
87.2 |
B+ |
3 |
S_1 |
C_1 |
1104 |
F |
street_2 |
167 |
81 |
80.4 |
B- |
4 |
S_1 |
C_1 |
1105 |
F |
street_4 |
159 |
64 |
84.8 |
B+ |
2. 写入
(a)csv格式
df.to_csv(‘data/new_table.csv‘)
#df.to_csv(‘data/new_table.csv‘, index=False) #保存时除去行索引
(b)xls或xlsx格式
#需要安装openpyxl
df.to_excel(‘data/new_table2.xlsx‘, sheet_name=‘Sheet1‘)
二、基本数据结构
1. Series
(a)创建一个Series
对于一个Series,其中最常用的属性为值(values),索引(index),名字(name),类型(dtype)
s = pd.Series(np.random.randn(5),index=[‘a‘,‘b‘,‘c‘,‘d‘,‘e‘],name=‘这是一个Series‘,dtype=‘float64‘)
s
a -0.152799
b -1.208334
c 0.668842
d 1.547519
e 0.309276
Name: 这是一个Series, dtype: float64
(b)访问Series属性
s.values
array([-0.15279875, -1.20833379, 0.6688421 , 1.54751933, 0.30927643])
s.name
‘这是一个Series‘
s.index
Index([‘a‘, ‘b‘, ‘c‘, ‘d‘, ‘e‘], dtype=‘object‘)
s.dtype
dtype(‘float64‘)
(c)取出某一个元素
将在第2章详细讨论索引的应用,这里先大致了解
s[‘a‘]
-0.15279874545981778
(d)调用方法
s.mean()
0.23290106551625706
Series有相当多的方法可以调用:
print([attr for attr in dir(s) if not attr.startswith(‘_‘)])
[‘T‘, ‘a‘, ‘abs‘, ‘add‘, ‘add_prefix‘, ‘add_suffix‘, ‘agg‘, ‘aggregate‘, ‘align‘, ‘all‘, ‘any‘, ‘append‘, ‘apply‘, ‘argmax‘, ‘argmin‘, ‘argsort‘, ‘array‘, ‘asfreq‘, ‘asof‘, ‘astype‘, ‘at‘, ‘at_time‘, ‘attrs‘, ‘autocorr‘, ‘axes‘, ‘b‘, ‘between‘, ‘between_time‘, ‘bfill‘, ‘bool‘, ‘c‘, ‘clip‘, ‘combine‘, ‘combine_first‘, ‘convert_dtypes‘, ‘copy‘, ‘corr‘, ‘count‘, ‘cov‘, ‘cummax‘, ‘cummin‘, ‘cumprod‘, ‘cumsum‘, ‘d‘, ‘describe‘, ‘diff‘, ‘div‘, ‘divide‘, ‘divmod‘, ‘dot‘, ‘drop‘, ‘drop_duplicates‘, ‘droplevel‘, ‘dropna‘, ‘dtype‘, ‘dtypes‘, ‘duplicated‘, ‘e‘, ‘empty‘, ‘eq‘, ‘equals‘, ‘ewm‘, ‘expanding‘, ‘explode‘, ‘factorize‘, ‘ffill‘, ‘fillna‘, ‘filter‘, ‘first‘, ‘first_valid_index‘, ‘floordiv‘, ‘ge‘, ‘get‘, ‘groupby‘, ‘gt‘, ‘hasnans‘, ‘head‘, ‘hist‘, ‘iat‘, ‘idxmax‘, ‘idxmin‘, ‘iloc‘, ‘index‘, ‘infer_objects‘, ‘interpolate‘, ‘is_monotonic‘, ‘is_monotonic_decreasing‘, ‘is_monotonic_increasing‘, ‘is_unique‘, ‘isin‘, ‘isna‘, ‘isnull‘, ‘item‘, ‘items‘, ‘iteritems‘, ‘keys‘, ‘kurt‘, ‘kurtosis‘, ‘last‘, ‘last_valid_index‘, ‘le‘, ‘loc‘, ‘lt‘, ‘mad‘, ‘map‘, ‘mask‘, ‘max‘, ‘mean‘, ‘median‘, ‘memory_usage‘, ‘min‘, ‘mod‘, ‘mode‘, ‘mul‘, ‘multiply‘, ‘name‘, ‘nbytes‘, ‘ndim‘, ‘ne‘, ‘nlargest‘, ‘notna‘, ‘notnull‘, ‘nsmallest‘, ‘nunique‘, ‘pct_change‘, ‘pipe‘, ‘plot‘, ‘pop‘, ‘pow‘, ‘prod‘, ‘product‘, ‘quantile‘, ‘radd‘, ‘rank‘, ‘ravel‘, ‘rdiv‘, ‘rdivmod‘, ‘reindex‘, ‘reindex_like‘, ‘rename‘, ‘rename_axis‘, ‘reorder_levels‘, ‘repeat‘, ‘replace‘, ‘resample‘, ‘reset_index‘, ‘rfloordiv‘, ‘rmod‘, ‘rmul‘, ‘rolling‘, ‘round‘, ‘rpow‘, ‘rsub‘, ‘rtruediv‘, ‘sample‘, ‘searchsorted‘, ‘sem‘, ‘set_axis‘, ‘shape‘, ‘shift‘, ‘size‘, ‘skew‘, ‘slice_shift‘, ‘sort_index‘, ‘sort_values‘, ‘squeeze‘, ‘std‘, ‘sub‘, ‘subtract‘, ‘sum‘, ‘swapaxes‘, ‘swaplevel‘, ‘tail‘, ‘take‘, ‘to_clipboard‘, ‘to_csv‘, ‘to_dict‘, ‘to_excel‘, ‘to_frame‘, ‘to_hdf‘, ‘to_json‘, ‘to_latex‘, ‘to_list‘, ‘to_markdown‘, ‘to_numpy‘, ‘to_period‘, ‘to_pickle‘, ‘to_sql‘, ‘to_string‘, ‘to_timestamp‘, ‘to_xarray‘, ‘transform‘, ‘transpose‘, ‘truediv‘, ‘truncate‘, ‘tshift‘, ‘tz_convert‘, ‘tz_localize‘, ‘unique‘, ‘unstack‘, ‘update‘, ‘value_counts‘, ‘values‘, ‘var‘, ‘view‘, ‘where‘, ‘xs‘]
2. DataFrame
(a)创建一个DataFrame
df = pd.DataFrame({‘col1‘:list(‘abcde‘),‘col2‘:range(5,10),‘col3‘:[1.3,2.5,3.6,4.6,5.8]},
index=list(‘一二三四五‘))
df
|
col1 |
col2 |
col3 |
一 |
a |
5 |
1.3 |
二 |
b |
6 |
2.5 |
三 |
c |
7 |
3.6 |
四 |
d |
8 |
4.6 |
五 |
e |
9 |
5.8 |
(b)从DataFrame取出一列为Series
df[‘col1‘]
一 a
二 b
三 c
四 d
五 e
Name: col1, dtype: object
type(df)
pandas.core.frame.DataFrame
type(df[‘col1‘])
pandas.core.series.Series
(c)修改行或列名
df.rename(index={‘一‘:‘one‘},columns={‘col1‘:‘new_col1‘})
|
new_col1 |
col2 |
col3 |
one |
a |
5 |
1.3 |
二 |
b |
6 |
2.5 |
三 |
c |
7 |
3.6 |
四 |
d |
8 |
4.6 |
五 |
e |
9 |
5.8 |
(d)调用属性和方法
df.index
Index([‘一‘, ‘二‘, ‘三‘, ‘四‘, ‘五‘], dtype=‘object‘)
df.columns
Index([‘col1‘, ‘col2‘, ‘col3‘], dtype=‘object‘)
df.values
array([[‘a‘, 5, 1.3],
[‘b‘, 6, 2.5],
[‘c‘, 7, 3.6],
[‘d‘, 8, 4.6],
[‘e‘, 9, 5.8]], dtype=object)
df.shape
(5, 3)
df.mean() #本质上是一种Aggregation操作,将在第3章详细介绍
col2 7.00
col3 3.56
dtype: float64
(e)索引对齐特性
这是Pandas中非常强大的特性,不理解这一特性有时就会造成一些麻烦
df1 = pd.DataFrame({‘A‘:[1,2,3]},index=[1,2,3])
df2 = pd.DataFrame({‘A‘:[1,2,3]},index=[3,1,2])
df1-df2 #由于索引对齐,因此结果不是0
(f)列的删除与添加
对于删除而言,可以使用drop函数或del或pop
df.drop(index=‘五‘,columns=‘col1‘) #设置inplace=True后会直接在原DataFrame中改动
|
col2 |
col3 |
一 |
5 |
1.3 |
二 |
6 |
2.5 |
三 |
7 |
3.6 |
四 |
8 |
4.6 |
df[‘col1‘]=[1,2,3,4,5]
del df[‘col1‘]
df
|
col2 |
col3 |
一 |
5 |
1.3 |
二 |
6 |
2.5 |
三 |
7 |
3.6 |
四 |
8 |
4.6 |
五 |
9 |
5.8 |
pop方法直接在原来的DataFrame上操作,且返回被删除的列,与python中的pop函数类似
df[‘col1‘]=[1,2,3,4,5]
df.pop(‘col1‘)
一 1
二 2
三 3
四 4
五 5
Name: col1, dtype: int64
df
|
col2 |
col3 |
一 |
5 |
1.3 |
二 |
6 |
2.5 |
三 |
7 |
3.6 |
四 |
8 |
4.6 |
五 |
9 |
5.8 |
可以直接增加新的列,也可以使用assign方法
df1[‘B‘]=list(‘abc‘)
df1
df1.assign(C=pd.Series(list(‘def‘)))
#思考:为什么会出现NaN?(提示:索引对齐)assign左右两边的索引不一样,请问结果的索引谁说了算?
|
A |
B |
C |
1 |
1 |
a |
e |
2 |
2 |
b |
f |
3 |
3 |
c |
NaN |
但assign方法不会对原DataFrame做修改
df1
(g)根据类型选择列
df.select_dtypes(include=[‘number‘]).head()
|
col2 |
col3 |
一 |
5 |
1.3 |
二 |
6 |
2.5 |
三 |
7 |
3.6 |
四 |
8 |
4.6 |
五 |
9 |
5.8 |
df.select_dtypes(include=[‘float‘]).head()
|
col3 |
一 |
1.3 |
二 |
2.5 |
三 |
3.6 |
四 |
4.6 |
五 |
5.8 |
(h)将Series转换为DataFrame
s = df.mean()
s.name=‘to_DataFrame‘
s
col2 7.00
col3 3.56
Name: to_DataFrame, dtype: float64
s.to_frame()
|
to_DataFrame |
col2 |
7.00 |
col3 |
3.56 |
使用T符号可以转置
s.to_frame().T
|
col2 |
col3 |
to_DataFrame |
7.0 |
3.56 |
三、常用基本函数
从下面开始,包括后面所有章节,我们都会用到这份虚拟的数据集
df = pd.read_csv(‘data/table.csv‘)
1. head和tail
df.head()
|
School |
Class |
ID |
Gender |
Address |
Height |
Weight |
Math |
Physics |
0 |
S_1 |
C_1 |
1101 |
M |
street_1 |
173 |
63 |
34.0 |
A+ |
1 |
S_1 |
C_1 |
1102 |
F |
street_2 |
192 |
73 |
32.5 |
B+ |
2 |
S_1 |
C_1 |
1103 |
M |
street_2 |
186 |
82 |
87.2 |
B+ |
3 |
S_1 |
C_1 |
1104 |
F |
street_2 |
167 |
81 |
80.4 |
B- |
4 |
S_1 |
C_1 |
1105 |
F |
street_4 |
159 |
64 |
84.8 |
B+ |
df.tail()
|
School |
Class |
ID |
Gender |
Address |
Height |
Weight |
Math |
Physics |
30 |
S_2 |
C_4 |
2401 |
F |
street_2 |
192 |
62 |
45.3 |
A |
31 |
S_2 |
C_4 |
2402 |
M |
street_7 |
166 |
82 |
48.7 |
B |
32 |
S_2 |
C_4 |
2403 |
F |
street_6 |
158 |
60 |
59.7 |
B+ |
33 |
S_2 |
C_4 |
2404 |
F |
street_2 |
160 |
84 |
67.7 |
B |
34 |
S_2 |
C_4 |
2405 |
F |
street_6 |
193 |
54 |
47.6 |
B |
可以指定n参数显示多少行
df.head(3)
|
School |
Class |
ID |
Gender |
Address |
Height |
Weight |
Math |
Physics |
0 |
S_1 |
C_1 |
1101 |
M |
street_1 |
173 |
63 |
34.0 |
A+ |
1 |
S_1 |
C_1 |
1102 |
F |
street_2 |
192 |
73 |
32.5 |
B+ |
2 |
S_1 |
C_1 |
1103 |
M |
street_2 |
186 |
82 |
87.2 |
B+ |
2. unique和nunique
nunique显示有多少个唯一值
df[‘Physics‘].nunique()
7
unique显示所有的唯一值
df[‘Physics‘].unique()
array([‘A+‘, ‘B+‘, ‘B-‘, ‘A-‘, ‘B‘, ‘A‘, ‘C‘], dtype=object)
3. count和value_counts
count返回非缺失值元素个数
df[‘Physics‘].count()
35
value_counts返回每个元素有多少个
df[‘Physics‘].value_counts()
B+ 9
B 8
B- 6
A 4
A+ 3
A- 3
C 2
Name: Physics, dtype: int64
4. describe和info
info函数返回有哪些列、有多少非缺失值、每列的类型
df.info()
<class ‘pandas.core.frame.DataFrame‘>
RangeIndex: 35 entries, 0 to 34
Data columns (total 9 columns):
# Column Non-Null Count Dtype
--- ------ -------------- -----
0 School 35 non-null object
1 Class 35 non-null object
2 ID 35 non-null int64
3 Gender 35 non-null object
4 Address 35 non-null object
5 Height 35 non-null int64
6 Weight 35 non-null int64
7 Math 35 non-null float64
8 Physics 35 non-null object
dtypes: float64(1), int64(3), object(5)
memory usage: 2.6+ KB
describe默认统计数值型数据的各个统计量
df.describe()
|
ID |
Height |
Weight |
Math |
count |
35.00000 |
35.000000 |
35.000000 |
35.000000 |
mean |
1803.00000 |
174.142857 |
74.657143 |
61.351429 |
std |
536.87741 |
13.541098 |
12.895377 |
19.915164 |
min |
1101.00000 |
155.000000 |
53.000000 |
31.500000 |
25% |
1204.50000 |
161.000000 |
63.000000 |
47.400000 |
50% |
2103.00000 |
173.000000 |
74.000000 |
61.700000 |
75% |
2301.50000 |
187.500000 |
82.000000 |
77.100000 |
max |
2405.00000 |
195.000000 |
100.000000 |
97.000000 |
可以自行选择分位数
df.describe(percentiles=[.05, .25, .75, .95])
|
ID |
Height |
Weight |
Math |
count |
35.00000 |
35.000000 |
35.000000 |
35.000000 |
mean |
1803.00000 |
174.142857 |
74.657143 |
61.351429 |
std |
536.87741 |
13.541098 |
12.895377 |
19.915164 |
min |
1101.00000 |
155.000000 |
53.000000 |
31.500000 |
5% |
1102.70000 |
157.000000 |
56.100000 |
32.640000 |
25% |
1204.50000 |
161.000000 |
63.000000 |
47.400000 |
50% |
2103.00000 |
173.000000 |
74.000000 |
61.700000 |
75% |
2301.50000 |
187.500000 |
82.000000 |
77.100000 |
95% |
2403.30000 |
193.300000 |
97.600000 |
90.040000 |
max |
2405.00000 |
195.000000 |
100.000000 |
97.000000 |
对于非数值型也可以用describe函数
df[‘Physics‘].describe()
count 35
unique 7
top B+
freq 9
Name: Physics, dtype: object
5. idxmax和nlargest
idxmax函数返回最大值所在索引,在某些情况下特别适用,idxmin功能类似
df[‘Math‘].idxmax()
5
nlargest函数返回前几个大的元素值,nsmallest功能类似
df[‘Math‘].nlargest(3)
5 97.0
28 95.5
11 87.7
Name: Math, dtype: float64
6. clip和replace
clip和replace是两类替换函数
clip是对超过或者低于某些值的数进行截断
df[‘Math‘].head()
0 34.0
1 32.5
2 87.2
3 80.4
4 84.8
Name: Math, dtype: float64
df[‘Math‘].clip(33,80).head()
0 34.0
1 33.0
2 80.0
3 80.0
4 80.0
Name: Math, dtype: float64
df[‘Math‘].mad()
16.924244897959188
replace是对某些值进行替换
df[‘Address‘].head()
0 street_1
1 street_2
2 street_2
3 street_2
4 street_4
Name: Address, dtype: object
df[‘Address‘].replace([‘street_1‘,‘street_2‘],[‘one‘,‘two‘]).head()
0 one
1 two
2 two
3 two
4 street_4
Name: Address, dtype: object
通过字典,可以直接在表中修改
df.replace({‘Address‘:{‘street_1‘:‘one‘,‘street_2‘:‘two‘}}).head()
|
School |
Class |
ID |
Gender |
Address |
Height |
Weight |
Math |
Physics |
0 |
S_1 |
C_1 |
1101 |
M |
one |
173 |
63 |
34.0 |
A+ |
1 |
S_1 |
C_1 |
1102 |
F |
two |
192 |
73 |
32.5 |
B+ |
2 |
S_1 |
C_1 |
1103 |
M |
two |
186 |
82 |
87.2 |
B+ |
3 |
S_1 |
C_1 |
1104 |
F |
two |
167 |
81 |
80.4 |
B- |
4 |
S_1 |
C_1 |
1105 |
F |
street_4 |
159 |
64 |
84.8 |
B+ |
7. apply函数
apply是一个自由度很高的函数,在第3章我们还要提到
对于Series,它可以迭代每一列的值操作:
df[‘Math‘].apply(lambda x:str(x)+‘!‘).head() #可以使用lambda表达式,也可以使用函数
0 34.0!
1 32.5!
2 87.2!
3 80.4!
4 84.8!
Name: Math, dtype: object
对于DataFrame,它在默认axis=0下可以迭代每一个列操作:
df.apply(lambda x:x.apply(lambda x:str(x)+‘!‘)).head() #这是一个稍显复杂的例子,有利于理解apply的功能
|
School |
Class |
ID |
Gender |
Address |
Height |
Weight |
Math |
Physics |
0 |
S_1! |
C_1! |
1101! |
M! |
street_1! |
173! |
63! |
34.0! |
A+! |
1 |
S_1! |
C_1! |
1102! |
F! |
street_2! |
192! |
73! |
32.5! |
B+! |
2 |
S_1! |
C_1! |
1103! |
M! |
street_2! |
186! |
82! |
87.2! |
B+! |
3 |
S_1! |
C_1! |
1104! |
F! |
street_2! |
167! |
81! |
80.4! |
B-! |
4 |
S_1! |
C_1! |
1105! |
F! |
street_4! |
159! |
64! |
84.8! |
B+! |
Pandas中的axis参数=0时,永远表示的是处理方向而不是聚合方向,当axis=‘index‘或=0时,对列迭代对行聚合,行即为跨列,axis=1同理
四、排序
1. 索引排序
df.set_index(‘Math‘).head() #set_index函数可以设置索引,将在下一章详细介绍
|
School |
Class |
ID |
Gender |
Address |
Height |
Weight |
Physics |
Math |
|
|
|
|
|
|
|
|
34.0 |
S_1 |
C_1 |
1101 |
M |
street_1 |
173 |
63 |
A+ |
32.5 |
S_1 |
C_1 |
1102 |
F |
street_2 |
192 |
73 |
B+ |
87.2 |
S_1 |
C_1 |
1103 |
M |
street_2 |
186 |
82 |
B+ |
80.4 |
S_1 |
C_1 |
1104 |
F |
street_2 |
167 |
81 |
B- |
84.8 |
S_1 |
C_1 |
1105 |
F |
street_4 |
159 |
64 |
B+ |
df.set_index(‘Math‘).sort_index().head() #可以设置ascending参数,默认为升序,True
|
School |
Class |
ID |
Gender |
Address |
Height |
Weight |
Physics |
Math |
|
|
|
|
|
|
|
|
31.5 |
S_1 |
C_3 |
1301 |
M |
street_4 |
161 |
68 |
B+ |
32.5 |
S_1 |
C_1 |
1102 |
F |
street_2 |
192 |
73 |
B+ |
32.7 |
S_2 |
C_3 |
2302 |
M |
street_5 |
171 |
88 |
A |
33.8 |
S_1 |
C_2 |
1204 |
F |
street_5 |
162 |
63 |
B |
34.0 |
S_1 |
C_1 |
1101 |
M |
street_1 |
173 |
63 |
A+ |
2. 值排序
df.sort_values(by=‘Class‘).head()
|
School |
Class |
ID |
Gender |
Address |
Height |
Weight |
Math |
Physics |
0 |
S_1 |
C_1 |
1101 |
M |
street_1 |
173 |
63 |
34.0 |
A+ |
19 |
S_2 |
C_1 |
2105 |
M |
street_4 |
170 |
81 |
34.2 |
A |
18 |
S_2 |
C_1 |
2104 |
F |
street_5 |
159 |
97 |
72.2 |
B+ |
16 |
S_2 |
C_1 |
2102 |
F |
street_6 |
161 |
61 |
50.6 |
B+ |
15 |
S_2 |
C_1 |
2101 |
M |
street_7 |
174 |
84 |
83.3 |
C |
多个值排序,即先对第一层排,在第一层相同的情况下对第二层排序
df.sort_values(by=[‘Address‘,‘Height‘]).head()
|
School |
Class |
ID |
Gender |
Address |
Height |
Weight |
Math |
Physics |
0 |
S_1 |
C_1 |
1101 |
M |
street_1 |
173 |
63 |
34.0 |
A+ |
11 |
S_1 |
C_3 |
1302 |
F |
street_1 |
175 |
57 |
87.7 |
A- |
23 |
S_2 |
C_2 |
2204 |
M |
street_1 |
175 |
74 |
47.2 |
B- |
33 |
S_2 |
C_4 |
2404 |
F |
street_2 |
160 |
84 |
67.7 |
B |
3 |
S_1 |
C_1 |
1104 |
F |
street_2 |
167 |
81 |
80.4 |
B- |
五、问题与练习
1. 问题
【问题一】 Series和DataFrame有哪些常见属性和方法?
【问题二】 value_counts会统计缺失值吗?
【问题三】 如果有多个索引同时取到最大值,idxmax会返回所有这些索引吗?如果不会,那么怎么返回这些索引?
【问题四】 在常用函数一节中,由于一些函数的功能比较简单,因此没有列入,现在将它们列在下面,请分别说明它们的用途并尝试使用。
【问题五】 df.mean(axis=1)是什么意思?它与df.mean()的结果一样吗?问题四提到的函数也有axis参数吗?怎么使用?
【问题六】 对值进行排序后,相同的值次序由什么决定?
【问题七】 Pandas中为各类基础运算也定义了函数,比如s1.add(s2)表示两个Series相加,但既然已经有了‘+‘,是不是多此一举?
【问题八】 如果DataFrame某一列的元素是numpy数组,那么将其保存到csv在读取后就会变成字符串,怎么解决?
2. 练习
【练习一】 现有一份关于美剧《权力的游戏》剧本的数据集,请解决以下问题:
(a)在所有的数据中,一共出现了多少人物?
(b)以单元格计数(即简单把一个单元格视作一句),谁说了最多的话?
(c)以单词计数,谁说了最多的单词?(不是单句单词最多,是指每人说过单词的总数最多,为了简便,只以空格为单词分界点,不考虑其他情况)
pd.read_csv(‘data/Game_of_Thrones_Script.csv‘).head()
|
Release Date |
Season |
Episode |
Episode Title |
Name |
Sentence |
0 |
2011/4/17 |
Season 1 |
Episode 1 |
Winter is Coming |
waymar royce |
What do you expect? They‘re savages. One lot s... |
1 |
2011/4/17 |
Season 1 |
Episode 1 |
Winter is Coming |
will |
I‘ve never seen wildlings do a thing like this... |
2 |
2011/4/17 |
Season 1 |
Episode 1 |
Winter is Coming |
waymar royce |
How close did you get? |
3 |
2011/4/17 |
Season 1 |
Episode 1 |
Winter is Coming |
will |
Close as any man would. |
4 |
2011/4/17 |
Season 1 |
Episode 1 |
Winter is Coming |
gared |
We should head back to the wall. |
【练习二】现有一份关于科比的投篮数据集,请解决如下问题:
(a)哪种action_type和combined_shot_type的组合是最多的?
(b)在所有被记录的game_id中,遭遇到最多的opponent是一个支?(由于一场比赛会有许多次投篮,但对阵的对手只有一个,本题相当 于问科比和哪个队交锋次数最多)
pd.read_csv(‘data/Kobe_data.csv‘,index_col=‘shot_id‘).head()
#index_col的作用是将某一列作为行索引
|
action_type |
combined_shot_type |
game_event_id |
game_id |
lat |
loc_x |
loc_y |
lon |
minutes_remaining |
period |
... |
shot_made_flag |
shot_type |
shot_zone_area |
shot_zone_basic |
shot_zone_range |
team_id |
team_name |
game_date |
matchup |
opponent |
shot_id |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
1 |
Jump Shot |
Jump Shot |
10 |
20000012 |
33.9723 |
167 |
72 |
-118.1028 |
10 |
1 |
... |
NaN |
2PT Field Goal |
Right Side(R) |
Mid-Range |
16-24 ft. |
1610612747 |
Los Angeles Lakers |
2000/10/31 |
LAL @ POR |
POR |
2 |
Jump Shot |
Jump Shot |
12 |
20000012 |
34.0443 |
-157 |
0 |
-118.4268 |
10 |
1 |
... |
0.0 |
2PT Field Goal |
Left Side(L) |
Mid-Range |
8-16 ft. |
1610612747 |
Los Angeles Lakers |
2000/10/31 |
LAL @ POR |
POR |
3 |
Jump Shot |
Jump Shot |
35 |
20000012 |
33.9093 |
-101 |
135 |
-118.3708 |
7 |
1 |
... |
1.0 |
2PT Field Goal |
Left Side Center(LC) |
Mid-Range |
16-24 ft. |
1610612747 |
Los Angeles Lakers |
2000/10/31 |
LAL @ POR |
POR |
4 |
Jump Shot |
Jump Shot |
43 |
20000012 |
33.8693 |
138 |
175 |
-118.1318 |
6 |
1 |
... |
0.0 |
2PT Field Goal |
Right Side Center(RC) |
Mid-Range |
16-24 ft. |
1610612747 |
Los Angeles Lakers |
2000/10/31 |
LAL @ POR |
POR |
5 |
Driving Dunk Shot |
Dunk |
155 |
20000012 |
34.0443 |
0 |
0 |
-118.2698 |
6 |
2 |
... |
1.0 |
2PT Field Goal |
Center(C) |
Restricted Area |
Less Than 8 ft. |
1610612747 |
Los Angeles Lakers |
2000/10/31 |
LAL @ POR |
POR |
5 rows × 24 columns
第1章 Pandas基础
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原文地址:https://www.cnblogs.com/hichens/p/13266777.html