Python | Lead and Trail padding of strings list

Sometimes, while working with string lists, we can have a problem in which we need to pad each string in list with a particular string. This type of problem can come in many places in web development domain. Let’s discuss certain ways in which this task can be performed.

Method #1 : Using list comprehension

This task can be performed using list comprehension. In this, we iterate each string element and reconstruct a new string list after adding required string at rear and front of each string.

# Python3 code to demonstrate working of
# Trail and lead padding of strings list
# using list comprehension

# initialize list
test_list = ["a", "b", "c"]

# printing original list
print("The original list : " + str(test_list))

# initialize pad_str
pad_str = 'gfg'

# Trail and lead padding of strings list
# using list comprehension
res = [pad_str + ele + pad_str  for ele in test_list]

# printing result
print("The String list after padding : " + str(res))

Output :

The original list : ['a', 'b', 'c']
The String list after padding : ['gfgagfg', 'gfgbgfg', 'gfgcgfg']

Method #2: Using list comprehension + string formatting

This task can also be performed using a combination of above functionalities. In this, we perform the task of padding using formatted string than + operator.

# Python3 code to demonstrate working of
# Trail and lead padding of strings list
# using list comprehension + string formatting

# initialize list
test_list = ["a", "b", "c"]

# printing original list
print("The original list : " + str(test_list))

# initialize pad_str
pad_str = 'gfg'

# Trail and lead padding of strings list
# using list comprehension + string formatting
temp = pad_str + '{0}' + pad_str
res =  [temp.format(ele) for ele in test_list]

# printing result
print("The String list after padding : " + str(res))

Output :

The original list : ['a', 'b', 'c']
The String list after padding : ['gfgagfg', 'gfgbgfg', 'gfgcgfg']