re-arrange column names in big dataframe code example

Example 1: pandas reorder columns

# Get column list in ['item1','item2','item3'] format 
df.columns
# [0]output: 
Index(['item1','item2','item3'], dtype='object')

# Copy just the list protion of the output and rearrange the columns 
cols = ['item3','item1','item2']

# Resave dataframe using new column order
df = df[cols]

Example 2: pandas reorder columns by name

#old df columns
df.columns
Index(['A', 'B', 'C', 'D'],dtype='***')
#new column format that we want to rearange
new_col = ['D','C','B','A'] #list of column name in order that we want

df = df[new_col]
df.columns
Index(['D', 'C', 'B', 'A'],dtype='***')
#new column order