Python Pandas Package: What is meant by dictionary

[zak100]

Hi,

I am following the link at:

https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.DataFrame.html

The link says that

Constructing DataFrame from a dictionary and then it shows the program:

import pandas as pd
d={'col1': [1, 2], 'col2':[3, 4]}
df = pd.DataFrame(data = d)
print (df)

I got the following output:

Quote

 col1  col2
0     1     3
1     2     4

I can't understand the concept of dictionary here. Somebody please guide me with a more meaningful example.

 

Zulfi.

 

 

[fiveworlds]

The python documentation uses the word dictionary to describe variables ithat are key-value pairs. 

The dictionary is defined here. 

d={'col1': [1, 2], 'col2':[3, 4]}

 

Edited August 30, 2020 by fiveworlds

[zak100]

Hi,

Thanks for your response. God blesses you.

 

You mean col1 and col2 are the keys and 1,2 and 3, 4 are the values. Keys are used for searching. But here one key i.e. Col1 or Col2 is corresponding to 2 values. How will we resolve the searching problem?

 

Zulfi.

[Ghideon]

3 hours ago, zak100 said:

You mean col1 and col2 are the keys and 1,2 and 3, 4 are the values. Keys are used for searching. But here one key i.e. Col1 or Col2 is corresponding to 2 values. How will we resolve the searching problem?

The keys are used to name the columns in the pandas DataFrame. Searching is then using pandas features i guess, example:

import pandas as pd
import sys
d={'col1': [1, 2], 'col2':[3, 4]}
df=pd.DataFrame(data = d)
print(df["col1"].min())
print(df["col1"].mean())
print('find and print the row where col1 has the value 1')
print(df[df["col1"]==1])

Typical output:

1
1.5
   col1  col2
0     1     3

Note: I assume the question is about Pandas since you link to Pandas. Creating DataFrame form a dictionary is just one (convenient) way to create a DataFrame. There are other means to create DataFrame. Searching and filtering the resulting dataframe is explained in the web site you linked to:

https://pandas.pydata.org/pandas-docs/stable/getting_started/intro_tutorials/03_subset_data.html#min-tut-03-subset

The section named "How do I filter specific rows from a DataFrame?" seems to be a good start.