String Manipulation Basics

What is String Data?

String means text. In real data, text is often messy:

Extra spaces: " John "
Wrong case: "JOHN" or "john"
Inconsistent format: "New York", "new york", "NEW YORK"

Access String Methods

Use .str to access text functions:

code.py

import pandas as pd

df = pd.DataFrame({
    'Name': ['  john  ', 'SARAH', 'Mike Smith']
})

# Use .str to access string methods
print(df['Name'].str.upper())

Change Text Case

code.py

df = pd.DataFrame({
    'Name': ['john doe', 'SARAH SMITH', 'Mike Jones']
})

# All uppercase
print(df['Name'].str.upper())
# JOHN DOE, SARAH SMITH, MIKE JONES

# All lowercase
print(df['Name'].str.lower())
# john doe, sarah smith, mike jones

# Title Case (First Letter Capital)
print(df['Name'].str.title())
# John Doe, Sarah Smith, Mike Jones

Remove Extra Spaces

code.py

df = pd.DataFrame({
    'Name': ['  john  ', '  sarah', 'mike  ']
})

# Remove spaces from both sides
df['Name'] = df['Name'].str.strip()
print(df)

Output:

    Name
0   john
1  sarah
2   mike

Also:

lstrip() - remove from left only
rstrip() - remove from right only

Get Text Length

code.py

df = pd.DataFrame({
    'Name': ['John', 'Sarah', 'Mike']
})

df['Name_Length'] = df['Name'].str.len()
print(df)

Output:

    Name  Name_Length
0   John            4
1  Sarah            5
2   Mike            4

Replace Text

code.py

df = pd.DataFrame({
    'Phone': ['123-456-7890', '987-654-3210']
})

# Remove dashes
df['Phone'] = df['Phone'].str.replace('-', '')
print(df)

Output:

        Phone
0  1234567890
1  9876543210

Check if Text Contains Something

code.py

df = pd.DataFrame({
    'Email': ['john@gmail.com', 'sarah@yahoo.com', 'mike@gmail.com']
})

# Find Gmail users
gmail_users = df[df['Email'].str.contains('gmail')]
print(gmail_users)

Output:

            Email
0  john@gmail.com
2  mike@gmail.com

Common String Methods

Method	What It Does
.str.upper()	ALL CAPS
.str.lower()	all lowercase
.str.title()	Title Case
.str.strip()	Remove spaces
.str.len()	Get length
.str.replace('a', 'b')	Replace text
.str.contains('x')	Check if contains

Key Points

Use .str before any text method
strip() removes extra spaces
upper(), lower(), title() change case
replace() finds and replaces text
contains() checks if text exists

What's Next?

Learn more string methods like split, extract, and starts/ends with.