pandas DataFrame Manipulation in Python – Operations & Editing (7 Examples)

This article illustrates how to edit pandas DataFrames in the Python programming language.

Setting up the Examples

import pandas as pd                                   # Import pandas library
my_df = pd.DataFrame({"A":["y", "x", "c", "v", "b"],  # Construct new pandas DataFrame
                      "B":range(25, 30),
                      "C":range(20, 15, - 1)})
print(my_df)                                          # Display pandas DataFrame
#    A   B   C
# 0  y  25  20
# 1  x  26  19
# 2  c  27  18
# 3  v  28  17
# 4  b  29  16

Example 1: Adding New Variable to pandas DataFrame

D = [1, 2, 3, 4, 5]                                   # Creating list object
print(D)
# [1, 2, 3, 4, 5]
df1 = my_df.assign(D = D)                             # Adding list as new column
print(df1)
#    A   B   C  D
# 0  y  25  20  1
# 1  x  26  19  2
# 2  c  27  18  3
# 3  v  28  17  4
# 4  b  29  16  5

Example 2: Merging Two pandas DataFrames

df2 = pd.DataFrame({"A":["c", "v", "b", "n"],         # Construct another pandas DataFrame
                    "D":range(50, 54),
                    "E":range(60, 64)})
print(df2)
#    A   D   E
# 0  c  50  60
# 1  v  51  61
# 2  b  52  62
# 3  n  53  63
df3 = pd.merge(my_df, df2, on = "A", how = "left")    # Left join
print(df3)
#    A   B   C     D     E
# 0  y  25  20   NaN   NaN
# 1  x  26  19   NaN   NaN
# 2  c  27  18  50.0  60.0
# 3  v  28  17  51.0  61.0
# 4  b  29  16  52.0  62.0

Example 3: Dropping Column from pandas DataFrame

df4 = my_df.drop("A", axis = 1)                       # Remove column from DataFrame
print(df4)
#     B   C
# 0  25  20
# 1  26  19
# 2  27  18
# 3  28  17
# 4  29  16

Example 4: Appending New Row to pandas DataFrame

add_row = [1, 2, 3]                                   # Creating list as new row
print(add_row)
df5 = my_df.copy()                                    # Adding new row to DataFrame
df5.loc[6] = add_row
print(df5)
#    A   B   C
# 0  y  25  20
# 1  x  26  19
# 2  c  27  18
# 3  v  28  17
# 4  b  29  16
# 6  1   2   3

Example 5: Concatenating Rows of Two pandas DataFrames

df6 = pd.DataFrame({"A":range(0, 5),                  # Construct another pandas DataFrame
                    "B":range(10, 15),
                    "C":range(20, 25)})
print(df6)
#    A   B   C
# 0  0  10  20
# 1  1  11  21
# 2  2  12  22
# 3  3  13  23
# 4  4  14  24
df7 = pd.concat([my_df, df6])                         # Appending two DataFrames
print(df7)
#    A   B   C
# 0  y  25  20
# 1  x  26  19
# 2  c  27  18
# 3  v  28  17
# 4  b  29  16
# 0  0  10  20
# 1  1  11  21
# 2  2  12  22
# 3  3  13  23
# 4  4  14  24

Example 6: Dropping Row from pandas DataFrame

df8 = my_df[my_df.B >= 27]                            # Removing particular rows
print(df8)
#    A   B   C
# 2  c  27  18
# 3  v  28  17
# 4  b  29  16

Example 7: Exchanging Values in pandas DataFrame

df8 = my_df.copy()                                    # Replace certain values in column
df8["B"] = df8["B"].replace(28, 1000)
print(df8)
#    A     B   C
# 0  y    25  20
# 1  x    26  19
# 2  c    27  18
# 3  v  1000  17
# 4  b    29  16

Further Resources

Furthermore, you may read the other posts on my website. Some tutorials are listed below.

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