Tuesday, June 23, 2020

Pandas: SQL Like pandas operations

Pandas's SQL Like operations such as WHERE clause.

=
!=
>=
str.contains()
&
|
.isin()
.isnull()
.notnull()
.duplicated()
.drop_duplicates()
.between


######


Pandas Common 3

Pandas common 3: filtering like WHERE clause in sql

Dataframe

In [ ]:
number,name,species,dob
1.0,joe,human,10-02-1977
2.0,john,human,01-04-1954
3.0,mike,human,04-29-1966
4.0,didi,cat,07-12-2019
5.0,aaron,human,09-08-1990
6.0,boo,dog,02-03-2015
7.0,ziggy,dog,08-09-2010
8.0,balou,gorilla,12-10-2005
9.0,"",""
In [248]:
import pandas as pd
df = pd.read_csv("test5.csv")
df
Out[248]:
number name species dob
0 1.0 joe human 10-02-1977
1 2.0 john human 01-04-1954
2 3.0 mike human 04-29-1966
3 4.0 didi cat 07-12-2019
4 5.0 aaron human 09-08-1990
5 6.0 boo dog 02-03-2015
6 7.0 ziggy dog 08-09-2010
7 8.0 balou gorilla 12-10-2005
8 9.0 NaN NaN NaN

"==" to produce similar effect as " = ".

can be done in .query() as well
In [249]:
df["name"] == "joe"
Out[249]:
0     True
1    False
2    False
3    False
4    False
5    False
6    False
7    False
8    False
Name: name, dtype: bool
In [250]:
#do a filter first then parse the boolean into the dataframe
df[df["species"] == "dog"]
Out[250]:
number name species dob
5 6.0 boo dog 02-03-2015
6 7.0 ziggy dog 08-09-2010
In [251]:
#assign to a parameter then selectively querying them
animal = df["species"] == "dog"
df[animal]
df [["species","name"]]
Out[251]:
species name
0 human joe
1 human john
2 human mike
3 cat didi
4 human aaron
5 dog boo
6 dog ziggy
7 gorilla balou
8 NaN NaN

"!=" as "!=" operator

can be done with .query() as well
In [252]:
animal = df["species"] != "dog"
df[animal]
Out[252]:
number name species dob
0 1.0 joe human 10-02-1977
1 2.0 john human 01-04-1954
2 3.0 mike human 04-29-1966
3 4.0 didi cat 07-12-2019
4 5.0 aaron human 09-08-1990
7 8.0 balou gorilla 12-10-2005
8 9.0 NaN NaN NaN

note: for date it works like string df["date"] >= "2020-01-01"

In [253]:
greater_date = df["dob"] >= "09-09-2005"
df[greater_date]
Out[253]:
number name species dob
0 1.0 joe human 10-02-1977
7 8.0 balou gorilla 12-10-2005
In [254]:
greater_number = df["number"] >= 4.0
df[greater_number]
Out[254]:
number name species dob
3 4.0 didi cat 07-12-2019
4 5.0 aaron human 09-08-1990
5 6.0 boo dog 02-03-2015
6 7.0 ziggy dog 08-09-2010
7 8.0 balou gorilla 12-10-2005
8 9.0 NaN NaN NaN

use "str.contains()" as "LIKE" operator

note: other noteworthy parameter for str.contains .. case=False and na=False
In [255]:
#like any
df["species"].str.contains("or")
Out[255]:
0    False
1    False
2    False
3    False
4    False
5    False
6    False
7     True
8      NaN
Name: species, dtype: object
In [256]:
#start with d
df["species"].str.startswith("d")
Out[256]:
0    False
1    False
2    False
3    False
4    False
5     True
6     True
7    False
8      NaN
Name: species, dtype: object
In [257]:
#end with n
df["species"].str.endswith("n")
Out[257]:
0     True
1     True
2     True
3    False
4     True
5    False
6    False
7    False
8      NaN
Name: species, dtype: object

"&" as "AND" operator

In [258]:
greater_number = df["number"] >= 4.0
species_type = df["species"] == "dog"
df[greater_number & species_type]
Out[258]:
number name species dob
5 6.0 boo dog 02-03-2015
6 7.0 ziggy dog 08-09-2010

" | " as "OR" operator in SQL

In [259]:
greater_number = df["number"] >= 4.0
species_type = df["species"] == "dog"
df[greater_number | species_type]
Out[259]:
number name species dob
3 4.0 didi cat 07-12-2019
4 5.0 aaron human 09-08-1990
5 6.0 boo dog 02-03-2015
6 7.0 ziggy dog 08-09-2010
7 8.0 balou gorilla 12-10-2005
8 9.0 NaN NaN NaN
In [260]:
greater_number = df["number"] == 4.0
species_type = df["species"] == "dog"
#comparing if greater is true and equal to true on specfies type. It only take row that is both row equal to true
df[greater_number == species_type]
Out[260]:
number name species dob
0 1.0 joe human 10-02-1977
1 2.0 john human 01-04-1954
2 3.0 mike human 04-29-1966
4 5.0 aaron human 09-08-1990
7 8.0 balou gorilla 12-10-2005
8 9.0 NaN NaN NaN
In [261]:
greater_number = df["number"] >= 4.0
species_type = df["species"] == "dog"
df[species_type]
Out[261]:
number name species dob
5 6.0 boo dog 02-03-2015
6 7.0 ziggy dog 08-09-2010
In [262]:
df["number"] == 4.0
Out[262]:
0    False
1    False
2    False
3     True
4    False
5    False
6    False
7    False
8    False
Name: number, dtype: bool
In [263]:
df["species"] == "dog"
Out[263]:
0    False
1    False
2    False
3    False
4    False
5     True
6     True
7    False
8    False
Name: species, dtype: bool

".isin()" as "in" operator

In [264]:
isin = df["species"].isin(["dog","gorilla"])
df[isin]
Out[264]:
number name species dob
5 6.0 boo dog 02-03-2015
6 7.0 ziggy dog 08-09-2010
7 8.0 balou gorilla 12-10-2005

"isnull()" as "IS NULL" operator

In [265]:
isnull = df["species"].isnull()
df[isnull]
Out[265]:
number name species dob
8 9.0 NaN NaN NaN

"notnull" as "IS NOT NULL" operator

In [266]:
notnull = df["species"].notnull()
df[notnull]
Out[266]:
number name species dob
0 1.0 joe human 10-02-1977
1 2.0 john human 01-04-1954
2 3.0 mike human 04-29-1966
3 4.0 didi cat 07-12-2019
4 5.0 aaron human 09-08-1990
5 6.0 boo dog 02-03-2015
6 7.0 ziggy dog 08-09-2010
7 8.0 balou gorilla 12-10-2005

"duplicated()"" somewhat similar to "select column,count() from table having count() > 1 group by column"

In [267]:
#keep = false is to print out every duplicates. Other parameters such as keep='first' or keep='last'
duplicate = df["species"].duplicated(keep = False)
df[duplicate]
Out[267]:
number name species dob
0 1.0 joe human 10-02-1977
1 2.0 john human 01-04-1954
2 3.0 mike human 04-29-1966
4 5.0 aaron human 09-08-1990
5 6.0 boo dog 02-03-2015
6 7.0 ziggy dog 08-09-2010

"drop_duplicates()" will drop the duplicates and print out what's left

In [268]:
dropduplicate = df["species"].drop_duplicates(keep=False)
dropduplicate
Out[268]:
3        cat
7    gorilla
8        NaN
Name: species, dtype: object

"between" as "BETWEEN" operator

In [269]:
between = df["number"].between(2,5)
df[between]
Out[269]:
number name species dob
1 2.0 john human 01-04-1954
2 3.0 mike human 04-29-1966
3 4.0 didi cat 07-12-2019
4 5.0 aaron human 09-08-1990

"loc[a:b]"" as select a range of index like bewtween for variables

In [270]:
betweenInd = df.loc['1':'3']
betweenInd
Out[270]:
number name species dob
1 2.0 john human 01-04-1954
2 3.0 mike human 04-29-1966
3 4.0 didi cat 07-12-2019

".query()" is simplify form of where clause

In [271]:
df.query('species == "human"')
Out[271]:
number name species dob
0 1.0 joe human 10-02-1977
1 2.0 john human 01-04-1954
2 3.0 mike human 04-29-1966
4 5.0 aaron human 09-08-1990
In [273]:
df.info()
<class 'pandas.core.frame.DataFrame'>
RangeIndex: 9 entries, 0 to 8
Data columns (total 4 columns):
 #   Column   Non-Null Count  Dtype  
---  ------   --------------  -----  
 0   number   9 non-null      float64
 1   name     8 non-null      object 
 2   species  8 non-null      object 
 3   dob      8 non-null      object 
dtypes: float64(1), object(3)
memory usage: 416.0+ bytes
In [285]:
df["number"].astype(int)
df.describe
df.describe()
df["name"].notnull()
df[df["name"].notnull()]
Out[285]:
number name species dob
0 1.0 joe human 10-02-1977
1 2.0 john human 01-04-1954
2 3.0 mike human 04-29-1966
3 4.0 didi cat 07-12-2019
4 5.0 aaron human 09-08-1990
5 6.0 boo dog 02-03-2015
6 7.0 ziggy dog 08-09-2010
7 8.0 balou gorilla 12-10-2005
In [ ]:
 

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Pandas: SQL Like pandas operations

Pandas's SQL Like operations such as WHERE clause. = != >= str.contains() & | .isin() .isnull() .notnull() ....