1. Drop the column. DataFrame has a method called drop() that removes rows or columns according to specify column(label) names and corresponding axis. ...
2. Delete the column. del is also an option, you can delete a column by del df['column name'] . ...
3. Pop the column.

within(df, rm(x))

is probably easiest, or for multiple variables:

within(df, rm(x, y))

Or if you're dealing with data.tables (per How do you delete a column by name in data.table?):

dt[, x := NULL]   # Deletes column x by reference instantly.

dt[, !"x"]   # Selects all but x into a new data.table.

or for multiple variables

dt[, c("x","y") := NULL]

dt[, !c("x", "y")]

df <- data.frame(a = 1:10, b = 2:11, c = 3:12)
df <- subset(df, select = c(a, c))​

df <- subset(df, select = -c(a, c))
​

df[, !(colnames(df) %in% c("x","bar","foo"))]
​

import pandas as pd

# Create a dataframe from a dict
df = pd.DataFrame({"a": [1,2,3], "b":[2,4,6]})
print("The DataFrame object before deleting the column")
print(df)
df.drop('a', inplace=True, axis=1)
print("The DataFrame object after deleting the column a")
print(df)​

DF <- data.frame(
  x=1:10,
  y=10:1,
  z=rep(5,10),
  a=11:20
)
drops <- c("x","z")
DF[ , !(names(DF) %in% drops)]

Or, alternatively, you can make a list of those to keep and refer to them by name :

keeps <- c("y", "a")
DF[keeps]

EDIT : For those still not acquainted with the drop argument of the indexing function, if you want to keep one column as a data frame, you do:

keeps <- "y"
DF[ , keeps, drop = FALSE]

drop=TRUE (or not mentioning it) will drop unnecessary dimensions, and hence return a vector with the values of column y.