Python Data Manipulation Cheat Sheet

When programming, keeping a solid ground and understanding how to manipulate data will save you a lot of time and effort. For this reason, here are some useful methods to remember, along with examples to clarify when they would be helpful.

Numbers

Method	Result
`min`, `max(number1, number2, ...)`	Returns the smallest/largest number among the provided arguments. For example, `min(3, 5)` returns `3` , `max(3, 5)` returns `5`.
`abs(number)`	Returns the absolute value of the given number. For example, `abs(-7)` returns `7`.

Examples:

Strings

Method	Result
`.lstrip(), .rstrip(), strip(args)`	Removes leading/trailing/both whitespace (or specified characters) from a string. By default, whitespace is removed.
`.find(sub)`	Returns the lowest index in the string where substring `sub` is found. Returns `-1` if `sub` is not found.
`.replace(arg1, arg2)`	Returns a new string where all occurrences of `arg1` are replaced by `arg2`.
`.split(sep=None)`, `.splitlines()`	Splits the string at the specified separator (`sep`) and returns a list of substrings. `.splitlines()` splits at line breaks.
`.partition(sep)`, `.rpartition(sep)`	Splits the string at the first/last occurrence of `sep`
`.endswith(sufix)`, `.startswith(prefix, start, end)`
`.count(sub)`	Number of occurrences of a substring

Examples:

text = "  Hello World  "
print(text.strip())            # Output: "Hello World"
print(text.lstrip())           # Output: "Hello World  "
print(text.rstrip())           # Output: "  Hello World"

sentence = "The quick brown fox jumps over the lazy dog"
print(sentence.find("fox"))    # Output: 16
print(sentence.replace("fox", "cat"))  # Output: "The quick brown cat jumps over the lazy dog"

lines = "line1\nline2\nline3"
print(lines.splitlines())      # Output: ['line1', 'line2', 'line3']

url = "https://example.com/page"
print(url.startswith("https")) # Output: True
print(url.endswith("page"))    # Output: True

print(sentence.count("the"))   # Output: 1 (case-sensitive)

Lists, Sets, Tuples

List = []
Tuple = ()
Set = {}

Method	Result
`.sort()`	Sorts the elements of the list in place. By default, it sorts in ascending order. For reverse order, use `.sort(reverse=True)`.
`.append(data)`	Adds an element to the end of the list.
`.remove(data)`	Removes the first occurrence of `data` from the list. Raises a `ValueError` if the element is not found.
`.pop(index=-1)`	Remove an element from a list while also returning it. It accepts one optional input which is the index of the element to remove. If no index is provided, then the last element in the list will be removed and returned.
`.insert(index, data)`	Add an element to a specific index in a list

Examples:

fruits = ['apple', 'banana', 'cherry']
fruits.sort()
print(fruits)                  # Output: ['apple', 'banana', 'cherry']

fruits.append('date')
print(fruits)                  # Output: ['apple', 'banana', 'cherry', 'date']

fruits.remove('banana')
print(fruits)                  # Output: ['apple', 'cherry', 'date']

last_fruit = fruits.pop()
print(last_fruit)              # Output: 'date'
print(fruits)                  # Output: ['apple', 'cherry']

fruits.insert(1, 'blueberry')
print(fruits)                  # Output: ['apple', 'blueberry', 'cherry']

Dictionaries

Method	Result
`dict1.update(dict2)`	Updates `dict1` with key-value pairs from `dict2`. If a key exists in both, the value from `dict2` overwrites the one in `dict1`.
`.keys(), .values(), .items()`	Return view objects that display a list of keys, values, or key-value pairs respectively. These views update dynamically when the dictionary changes.
`.get(key, default=None)`	Returns the value for `key` if `key` is in the dictionary, otherwise returns `default` (which defaults to `None`).
`.pop(key)`	The method takes a key as an argument and removes it from the dictionary. At the same time, it also returns the value that it removes from the dictionary.

Examples:

# Creating dictionaries
person = {'name': 'Alice', 'age': 30}
updates = {'age': 31, 'city': 'New York'}

# Update dictionary
person.update(updates)
print(person)
# Output: {'name': 'Alice', 'age': 31, 'city': 'New York'}

# Accessing keys, values, and items
print(list(person.keys()))    # Output: ['name', 'age', 'city']
print(list(person.values()))  # Output: ['Alice', 31, 'New York']
print(list(person.items()))   # Output: [('name', 'Alice'), ('age', 31), ('city', 'New York')]

# Using get() with and without default
print(person.get('name'))         # Output: Alice
print(person.get('country', 'USA'))  # Output: USA

# Pop a key from dictionary
age = person.pop('age')
print(age)                        # Output: 31
print(person)                     # Output: {'name': 'Alice', 'city': 'New York'}