Archive
Python: Pandas Lesson 9
Learning : Pandas Commands
Subject: Zoo Management System – P3
In this lesson we will write two functions in our Zoo Management System-ZMS, first one to load the data file (we assume we have our data file in the same directory of the .py file.) and the second one is to display a sample 5 rows from the data. We will write each function and test it then we will add it to our main app user_choice() section and will try it from there. At the end of this post you can find a screen shot of the user_choice() code with two function in place.
Also I would like to emphasize that I am not using any try .. exception block in this system, so I am expecting that the user will enter a valid data.
Load New File: As far we want to be simple in this lesson, we will assume that we have a file named ‘data_file_zoo.csv’ and that it stored in the same directory as our source file .py, so we will not cover the [find file code] to change or select other file in other directory.(maybe in version 2.0 of this app if we want to upgrade it. ).
Enhancement ides:
1. Giving the user the ability to change the path and the file.
2. User can start form new empty file and create the columns and data of his new data file.
def load_file()
def load_file() :
filename=’data_file_zoo.csv’
global df
df = pd.read_csv(filename)
print(‘\n\n *** File Been Loaded *** \n’)
input(‘\n ** Press any key to continu .. . . ‘)
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Show sample data: After loading the data into a df, and we set the df as a global variable so we can use it any-where in our application. So to print-out a sample data we will use coming code.
get_sample_data(df2)
def get_sample_data(df2):
clear() # To clear the terminal.
print(‘\n\n Sample Data from .. \n’,df2.sample(5))
input(‘\n ** Press any key to continue .. . . ‘)
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Here is the two function in the def user_coice(u_choice):
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Summary: At this point we have the menu and two functions, each time we run the app we need to select first number 1 to load the data into a df, the idea behind this was to give the user the opportunity to select any data file from any path, but in this stage the data file will be static in the code. this feature will be in version 2.0 After loading the data we can select number 2 from the menu ( Show sample data ).
And here is a run screen shot..
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In coming Next Post .. in coming post we will cover more functioins in our system. We will check the columns name, seeing the data type of each column and sorting the data in the data frame.
:: Pandas Lessons Post ::
| Lesson 1 | Lesson 2 | Lesson 3 | Lesson 4 |
| Lesson 5 | Lesson 6 | Lesson 7 | Lesson 8 |
| Lesson 9 |
Follow me on Twitter..Python: Pandas Lesson 8
Learning : Create simple zoo application P2
Subject: Zoo Management System – user_choice()
In Part1 we start with menu function and we said it will return the user input that represent the action he select. In this post we will write the choice loop code to determin the action we need to take and we will say if the user enter q or Q the we will exit, to do this i am adding this line in the end of the def the_menu()
return input(‘\n Select from the menu (”q” to quit): ‘)
After the_menu and whatever user chose we need to perform an action, here is another function def user_choice(): we will pass a variable to it and with some if statements other functions will be called.
User Choice function
def user_choice(u_choice):
if u_choice ==’1′ :
#Load new CSV.
pass
if u_choice ==’2′ :
# show data sample.
pass
if u_choice ==’3′ :
# show data column .
pass
if u_choice ==’4′ :
# data type.
pass
if u_choice ==’5′ :
# Sort based on user column selection.
pass
if u_choice ==’6′ :
#Missing Data.
pass
if u_choice ==’7′ :
# Add new Record.
pass
if u_choice ==’8′ :
# Edit a record.
pass
if u_choice ==’9′ :
# Delete a Record.
pass
if u_choice ==’10’ :
# Save the file.
pass
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and to keep the application running until the user enter we will use the while block to do this, here is the code:
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Starting from the coming lesson we will start to write the functions for each item in our menu, we may add new functions or renaming some and we may not going in order just pick one and work with. Let’s see what will happen then.
:: Pandas Lessons Post ::
| Lesson 1 | Lesson 2 | Lesson 3 | Lesson 4 |
| Lesson 5 | Lesson 6 | Lesson 7 | Lesson 8 |
| Lesson 9 | Lesson 10 | Lesson 11 | Lesson 12 |
Python: Pandas Lesson 7
Learning : Create simple zoo application P1
Subject: The Menu and functions names
Althought we mostly using pandas in reading datafile and analysing it, Here we are thinking as if we have an interface for an application, and we are offering some menu and function to the user so he can use the apps.
As we went throught learnning pandas and from all past lessons we saw alot’s of functions and commands that are enuph to start developing a small application to manage our zoo data. Starting from this post we will bulid parts of our application, so lets start.
The Menu The menu is the way or the tool that will help the user to perform deffernt action on the data. Here is the function of the the_menu and it will return the user selection.
Althought we mostly using pandas in reading datafile and analysing it, but Here we are think as if we have an interface of application, and the we are offering a menu to the user were he can select a function user will
The Menu
def the_menu ():
print(‘\n ::—–{ The menu }—-::’)
print(‘1. Load New csv File’)
print(‘2. Show Sample Data’)
print(‘3. Show Columns’)
print(‘4. Data Type’)
print(‘5. Sort.’)
print(‘6. Missing Data’)
print(‘7. Add New Record.’)
print(‘8. Edit a record.’)
print(‘9. Delete a Record.’)
print(’10. Save the File.’)
return (input(‘\n Enter your selection: ‘))
# calling the menu.the_menu()
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def the_menu(): The code above will print our menu on the screen and asking the user to select the action and return a number of the menu. From there we will run other functions, we may change or add to the menu if we need to.
First I will define each menu-line to have an overall view of the functionality in the app:
1. Load New csv File: We will ask the user to write the file name he want to upload, and we will assume that the file is in the same directory and if the file not exist we will create one.
2. Show Sample Data: Print out sample data from the dataframe using df.sampl().
3. Show Columns: List all the columns in the dataframe.
4. Data Type: Show the data Type of each column.
5. Sort: The user will select the sorting column.
6. Missing Data: This command will give the user a report of how many data are available in the columns and if there is any missing data.
7. Add New Record: Adding new row to the data file.
8. Edit a record: Editing a row.
9. Delete a Record: Deleting a row from the data file.
10. Save the File To save the file, and we will save it under new name.
Whats in the next lesson:
:: Writing the menu selection loops.
:: Writing the first two functions in the application.
:: Pandas Lessons Post ::
| Lesson 1 | Lesson 2 | Lesson 3 | Lesson 4 |
| Lesson 5 | Lesson 6 | Lesson 7 | Lesson 8 |
| Lesson 9 | Lesson 10 | Lesson 11 | Lesson 12 |
Python: Pandas Lesson 6
Learning : Panda Lesson 6
Subject: Pass variable to df
In this post we will cover some commands that we will re-use in a coming post were we will start to develop a small system/app to do full managing of our zoo file. currently i am putting the BluePrint of the app, basically the menu will have these functions:
The Menu: [load, view, add-edit-delete, sort, missing data, save to csv …], so lets start..
If we want to add new row to our dataframe, first we need to know our columns name. In our case data file zoo here is the column we have:
( animal, id, water_need, supervisor, cage_no, years ), at this point we will do this as static variable, but in coming lesson we will use an interactive sample.
So, we will write a dictionary that hold our new_row and append it to the dataframe.
Add new row to the datafram
new_row={‘animal’:’Koala’,’id’:5555,’water_need’:99,’supervisor’:’na’,’cage_no’:55,’years’:10}
df=df.append([new_row])
print(‘\n\n The df after adding one new row.\n’,df)
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You can see that there is a problem here, the id of our new row was entered manually (in this example) but we need this to be automatic and to do so we must first get the max value in the id column, add 1 to it then use it for the new entry. So we need to add this code:
next_id=df[‘id’].max() + 1
new_row={‘animal’:’koala’,’id’:next_id,’water_need’:99,’supervisor’:’na’,’cage_no’:55,’years’:10}
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To delete a row, we simply re-define the df without that row we want to delete. Say we want to delete the row that has id = 1020. The id is a primary key in our data-set and there is no duplicated numbers in id column so we can use it to identify a specific row. I assume that we know that we read the datafram and we want to delete the row id number 1020, here is the code:
Delete the row with id = 1020
df=df[df.id !=1020]
print(‘\n\n df after deleting row id:1020\n’,df)
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At the first paragraph i was talking about writing an app that fully manage the zoo file, so if the user want to read the rows based on a particular selection like : what are the animals in the cages number 2,5 and 8. Here is the code :
Animals in cage no 2,5 and 8
cage_arr=[2,5,8]
print(‘\n\n Animals in cages no.’,cage_arr,’\n’,df.loc[df[‘cage_no’].isin(cage_arr)])
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:: Pandas Lessons Post ::
| Lesson 1 | Lesson 2 | Lesson 3 | Lesson 4 |
| Lesson 5 | Lesson 6 | Lesson 7 | Lesson 8 |
| Lesson 9 | Lesson 10 | Lesson 11 | Lesson 12 |
Python: Pandas more commands
Learning : Pandas more commands
Subject: DataFrame Simple Statistics
In this post we will just go through some commands in pandas that related to simple statistics of dataframe, in coming table first we will list down all the commands then will see each in cation.
| Function | Description |
| 1. sum() | Get the sum of the value |
| 2. cumsum() | cumsum() is used to find the cumulative sumvalue over any axis. Each cell is populated with the cumulative sum of the values on upper cells. |
| 3. count() | counting the NaN in the DataFrame. |
| 4. mean() | |
| 5. median | |
| 6. std() | Standard deviation measures the spread of the data about the mean value. |
| 7. max() | Return the maximum value in each column. |
| 8. min() | Return the minimum value in each column. |
| 9. prod() | Return the value of product operation of the items in the column. (works only for number columns) |
| 10. Cumprod() | Return the number in the cell * all the cells over it. |
| 11. abs() | Returns the absolute value of the column and it is only applicable to numeric columns. |
| 12. mode() | It returns the most repeated value in the column. |
1. sum() Using command as: print(df.sum()) it will return a sum of columns, if contain numaric then it will be a normal sum, if it is string return a string contain all as one string without spaces.
In our cas (data_file_zoo) the only practical result is the water-need where it represent the total amout of water we need in our zoo. So to get the sum of one column we can write it as: df[column name].sum()
print(‘\n\n Total amout of water we need is: ‘, df[‘water_need’].sum())
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2. cumsum() Using command as: print(df.cumsum()) cumulative sumvalue will return the number in the cell + the sum of all the cells over it, we may need this function in a data analysis.
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3. count() Using command as: print(df.count()), this function gives us the total data in each columns, so we know how many NaN or empty cells are in our table.
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4. mean() Using command as: print(df.mean()), Thw Arithmetic Mean is the average of the numbers in the df for each columns.
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5. median() Using command as: print(df.mediam()), in a sorted list
median will return the middle value, If there is an even number of items in the data set, then the median is the mean (average) of the two middlemost numbers. We can get the median of the specific Column.
# median of water_need column..
print(‘\n\n Median of the Water Need: ‘,df.loc[:,”water_need”].median()
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6. sdt() Using command as: print(df.std()), it is the Standard deviation of the dataframe, or columns in the df.
The standard deviation measures the spread of the data about the mean value. It is useful in comparing sets of data which may have the same mean but a different range. In our example here (zoo file) some functions is not given the meaning that we may need, but if we have a data from statistical modeled or other scientific field this std() sure will be helpful.
7. max() Using command as: print(df.max()), return the maximum value in each column. If we want the max. value in a specific column then we use theis code:
print(‘\n\n’,df.loc[:,”water_need”].max())
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8. min() Using command as: print(df.min()), same as max, the min() will return the minimum value in the df for each column, and we can get the min for only one column by using:
print(‘\n\n’,df.loc[:,”water_need”].min())
9. prod() Using command as: print(df.prod()), return the value of product operation of the items in the column. (works only for number columns)
10. cumprod() Using command as: print(df.cumprod()), cumulative product will return the number in the cell * all the cells over it.
To show this i will use a Series of numbers and apply cumprod.
cumprod()
some_value = pd.Series([2, 3, 5, -1, 2])
print(‘\n\n some_value in a column.\n’,some_value)
print(‘\n\n some_value.cumprod()\n’,some_value.cumprod())
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11. abs() Using command as: print(df.abs()), It returns the absolute value of the column and it is only applicable to numeric columns.
12. mode() Using command as: print(df.mode()), It returns the most repeated value in the column.
Find the most repeated value:
print(‘\n\n Function: df.count()\n’,df.mode())
# mode of the specific column
df.loc[:,”animal”].mode()
:: Pandas Lessons Post ::
| Lesson 1 | Lesson 2 | Lesson 3 | Lesson 4 |
| Lesson 5 |
Python: Pandas Lesson 5
Learning : Pandas Lesson 5
Subject: Columns rename and missing data.
We are still in the same track looking after commands that help us in managing and formatting the dataframe. In most cases, we will have a data file from the net, or from a source that may not consider formatting or standardization as his/their concern, or we may find a lots of missing data in the file. In this post we will go through some lines that will make the file in better shape.
Columns, First thing we will look at is the head of the data table. So First, check your data columns with this code:
print(‘\n\n Current columns of the data.\n’,df3.columns)
Now we have the a list of the columns in our datafile, and we can change any of them just to give a more clear meaning or any other purpose. I found that using rename method and passing new columns names as dictionary is better because we can rename without order also not stick to rename them all.
df.rename(columns={‘animal’:’Animal-Kind’,’id’:’ID’,’cage_no’:’InCage’}, inplace=True)
print(‘\n\n Table with new renaming columns .\n’,df3)
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I just forgot to add .sample(6) so we will just have sample data, but anyway the new header is there and we use inplace = True so this new header will stay with us in df3.
Missing Data: This is the biggest challenge in any data file, some time the application that used to fills the form, or the person who entering the data or for any other reasons they are not handling the missing data in a standard way, so you may find just empty field, or ‘NA’ or dummy numbers like (0000), or (-0) or dashes (—). Handling such case is realy depending on the customer you are working for, like what they want to put/write in each empty field, now we are just talking about filling with standard key.
In coming code we are saying to pandas: whenever you found NaN replace it with ‘NA’
new_df=df3.fillna(‘NA’)
print(‘\n\n Replace NaN with NA.\n’new_df)
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Note This: I will go to our data_file_zoo.csv and just add more NaN to some fields so our coming case will be meaningful.
Our data_file_zoo.csv has 6 columns, animal, id are primary keys and can’t be empty, so there MUST be filled. Now for the other columns I will say for each of columns if the data is NaN then we will replace it with:(MD:Missinf Data, NA:Not Available and – for numbers )
water_need : MD
supervisor : NA
InCage : –
years : –
Note That we MUST use the same columns name in the df we are working with.
Here is the code:
Replacing Missing Data
new_df=df2.fillna({‘water_need’:’MD’, ‘supervisor’:’NA’,’InCage’: ‘-‘ ,’years’:’-‘})
print(‘\n\n’,new_df)
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(I mark the replacing fields.)
Let’s say we notes that some data in water_need column is not logical, like if we know it can’t be 600, so we just want to replace any number biger that or equal to 600 in that column ot ‘err’. Code here..
Code to change some value based on a condition.
df2.loc[df2[‘Water’] == 600, [‘Water’]] = ‘err’
print (‘\n\n change 600 to err./n’,df2)
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:: Pandas Lessons Post ::
| Lesson 1 | Lesson 2 | Lesson 3 |
| Lesson 4 | Lesson 5 |
Python: Pandas Lesson 4
Learning : Panda Lesson 4
Subject: DataFrame Columns: Hide, Drop, rename
We still workinng on dataframe and columns, we will go thrght some function and at the end I will just add a line to save the dataframe in a new CSV file. So let’s start.
We still working on our data_file_zoo.csv and here i am copying the column we have in the file or in our df.
print(‘\n\n Columns in thedataFrame..\n’,df.columns)
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Now we have a list of columns in our DataFrame, some time we want to hide a column, here we will creat a variable and whenever we call this variable the column will not be shone on the screen.
Hide column ‘supervisor’
In this line we will set a variable to hide supervisor column, and just for sceen-shop we will present 6 random rows
hide_supervisor=df.drop([‘supervisor’], axis=1)
print(‘\n\n Sample data after hiding supervisor column\n’,hide_supervisors.sample(6))
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In the upper case, we may have a password column or some key information column that we don’t want to be shown in the dataframe, then it’s good idea to create a DataFrame without this column an use it.
If we have a dataframe and we are examining some thing and don’t want to show all columns every time we print the df, so just show (say three) columns. To do this, first we will print the columns names so we know what we have in the df, then using coming code we will select whatever we want to show.
animal_cage_years=df[[‘animal’,’cage_no’,’years’]]
print(‘\n\n Show selected Columns from df\n’,animal_cage_years.sample(6))
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Now we will drop a column from the df, I will select ‘supervisor’, just like this:
print(‘\n\n Drop column ”supervisor” form the df’)
print(df.drop([‘supervisor’],axis=1))
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To be Aware: In the above case, if we use the command on df and we add inplace=True then this will change the df, so any time we calling the df it will be without the ‘supervisor’ column. Here is the code..
df.drop([‘supervisor’], inplace=True, axis=1)
print(‘\n\n’,df)
If we want to hide more than one columns we just add them in the command like this:
hide_years_cages=df.drop([‘years’,’cage_no’], axis=1)
print(hide_years_cages.sample(6))
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If we want to check wither or not a df contain column c_name if yes hide-it else print ‘Column not found’.
If column ‘cage_no’ in df hide it.
if ‘cage_no’ in df.columns:
hide_cage = df.drop([‘cage_no’], axis=1)
print(‘\n\n’,hide_cage.sample(6))
else:
print(‘Column not found’)
and we can in the else block just showing another dataframe.
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:: Pandas Lessons Post ::
| Lesson 1 | Lesson 2 | Lesson 3 | Lesson 4 |
| Lesson 5 |
Python: Pandas Lesson 3
Learning : Pandas Lesson 3
Subject: dataframe (sort, where and filters)
In my Last post Pandaas Lesson 2, we show some commands that will output part of our dataframe (df) such as if we want to output the information we have about lions, or other animals in the Zoo file. Or to see what aminals fell under particular supervisor. Also I try to add a print statment over each output table to show/describe the table content.
In theis Lesson, or let’s say in this post I will share another bunch of commands dealing with one table of data. We will keep using our Zoo data file. So first I wll call the dataframe df.
import pandas as pd
file_name=’data_file_zoo.csv’
df=pd.read_csv(file_name, delimiter=’,’)
print(‘\n Data from Zoo file..’,df)
So, if we want to sort the data based on supervisor name.
df.sort_values(‘supervisor’, inplace=True)
print(‘\n\n Sorted data with Supervisor Name\n’,df)
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First thing to notes that we have two group of supervisors name ‘peter’ one with small ‘p’, another with Big ‘P’. Another thing to see that we have some ‘lions’ with NaN under supervisor, this meas there is no data in that feilds. I will not change this now, let’s do this in another lesson.
So, let’s sort the data now with anumal type.
df.sort_values(‘animal’,inplace=True)
print(‘\n\n Sort with animal type.\n’,df)
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If we want to print all animal data under mark supervision, other data will be shown as NaN.
mark_supervision = df[‘supervisor’]==’mark’
df.where(mark_supervision, inplace = True)
print(‘\n\n Any rows else than Mark as supervisore will be as NaN\n’,df)
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If we want to add another filter to the upper dataframe to show animals under mark supervision if the animal age is more than 7.
age_biger_7 = df[‘years’] >7
df.where(mark_suoervision & age_biger_7, inplace = True)
print(‘\n\n Only rows under mark supervision if animal age > 7 \n’,df)
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:: Pandas Lessons Post ::
| Lesson 1 | Lesson 2 | Lesson 3 | Lesson 4 |
| Lesson 5 |
Python: Pandas Lesson
Learning : DataFrame and some commands
Subject: Pandas printing selected rows
First thing we will do today, we will add another coloumn to our CSV data_file_zoo.csv, we will add ‘years’ this will be hwo old each animal in the zoo is.
File_Name: data_file_zoo.csv
animal,id,water_need,supervisor,cage_no,years
elephant,1001,500,Peter,5,5
elephant,1002,600,John,5,4
elephant,1003,550,Peter,5,4
tiger,1004,300,mark,4,8
tiger,1005,320,mark,4,9
tiger,1006,330,peter,3,5
tiger,1007,290,mark,3,3
tiger,1008,310,D.J,4,4
zebra,1009,200,D.J,8,
zebra,1010,220,D.J,9,8
zebra,1011,240,D.J,9,7
zebra,1012,230,mark,8,6
zebra,1013,220,D.J,8,3
zebra,1014,100,D.J,9,4
zebra,1015,80,peter,9,4
lion,1016,420,,1,9
lion,1017,600,D.J,1,8
lion,1018,500,,2,4
lion,1019,390,,2,5
kangaroo,1020,410,peter,7,8
kangaroo,1021,430,D.J,7,6
kangaroo,1022,410,mark,7,1
As we just update out file, we need to load it to the memory by calling the df (dataframe), this will happen once we run our code.
Here is a screen shot of the new data using print(df)
Lets say we want to know how many animals are numder 6 years. Here we will use df.loc to locate what we are looking for.
age_less_6 = df.loc[(dfyears<6)]
# To print we may use this:
print(‘ we have {} animals less than 6 years’.format(len(age_less_6)))
Now, we want to print only lion rows:
lino_rows = df.loc[(df.animal==’lion’)]
Here is only rows with animal name ‘elephants’:
elephant_rows=df.loc[(df.animal==’elephant’)]
Now let’s print only the rows with lion and elephants:lion_and_elephant = df.loc[(df.animal==’lion’) | (df.animal == ‘elephant’)]
What if we want all the data but not the rows with lino or elephant.
all_exclude_lion_elephant=df.loc[(df.animal !=’lion’) & (df.animal !=’elephant’)]
:: Pandas Lessons Post ::
| Lesson 1 | Lesson 2 | Lesson 3 | Lesson 4 |
| Lesson 5 |
Python: Pandas Lessons
Learning : DataFrame and some commands
Subject:
This is my first hours in Pandas, until now thing are going smooth. I am using pythonanywhere on my PC, and jupyterlab on my galaxy tab S4.
In this post and coming once under name Pandas Lesson I will write some commands and what-ever I think I may need.
So, first thing we need a csv file with data to play with, so I search for some thing simple, i found one with zoo data!, I add two new column to it. so lets see it.
File_Name: data_file_zoo.csv
animal,id,water_need,supervisor,cage_no
elephant,1001,500,Peter,5
elephant,1002,600,John,5
elephant,1003,550,Peter,5
tiger,1004,300,mark,4
tiger,1005,320,mark,4
tiger,1006,330,peter,3
tiger,1007,290,mark,3
tiger,1008,310,D.J,4
zebra,1009,200,D.J,8
zebra,1010,220,D.J,9
zebra,1011,240,D.J,9
zebra,1012,230,mark,8
zebra,1013,220,D.J,8
zebra,1014,100,D.J,9
zebra,1015,80,peter,9
lion,1016,420,,1
lion,1017,600,D.J,1
lion,1018,500,,2
lion,1019,390,,2
kangaroo,1020,410,peter,7
kangaroo,1021,430,D.J,7
kangaroo,1022,410,mark,7
I add the ” supervisor and cage_no ” to the original file so we will have more room to manipulate.
First Command: first thing we need to call pandas library using import, and set the file name and dataframe.
import pandas as pd
file_name=’data_file_zoo.csv’
df=pd.read_csv(file_name, delimiter=’,’)
We will use this part for all our initialization part
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Other Command: Here are other commands that works with dataframe df.
| print(df) | Will print out all the data from the file. |
| print (df.head()) | Will print first 5 rows |
| print (df.tail()) | Will print last 5 rows |
| print (df.sample(3)) | Will print random 3 rows from the dataframe. |
| print(df.columns) | Will print the columns in the file |
| print (df[[‘id’,’animal’,’cage_no’]]) | Print only the data from column you want |
| print (df[[‘id’,’animal’,’cage_no’]].sample(3)) | Print random 3 rows of only ‘id’,’animal’,’cage_no’ columns |
| print (df[df.animal==’lion’]) | Get all the rows with animal name = lion . case sensitive |
| print(df.head()[[‘animal’,’id’]]) | Print first five rows of only animal and id |
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Wrapped up: This is a step one, pandas has many to read about and to learn, I start this initiative just for my self, and i select the hard way to do this, this is not important to my current job, this is nothing that any body will ask me about, but i want to learn and I think i will go further in this self-taught learning sessions..
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Update on: 29/7/2019
:: Pandas Lessons Post ::
| Lesson 1 | Lesson 2 | Lesson 3 | Lesson 4 |
| Lesson 5 |
Taking pictures is not my main daily practices, but when i start playing with my camera, i really enjoy my self.
Thanks for visiting my Space..
Ali's Photography Space... 