Python & Data Science Cheat Sheet Vocabulary

150 vocabulary flashcards covering Python basics, pandas, NumPy, scikit-learn, matplotlib, and related data science tools.

Integer (int)

Whole number data type, e.g., 1 or -3.

Float (float)

Floating-point number data type, e.g., 1.2 or -0.5.

String (str)

Sequence of characters enclosed in quotes, like "Hello".

Boolean

Logical value representing True or False.

List

Ordered, mutable collection enclosed in square brackets [].

Dictionary

Unordered collection of key–value pairs in curly braces {}.

Variable assignment

Binding a name to a value using the = operator.

f-string

Formatted string literal prefixed with f that supports inline expressions.

Indexing

Accessing a single element of a sequence by position (e.g., lst[0]).

Slicing

Extracting a subsequence using start:stop syntax (e.g., lst[1:3]).

append()

List method that adds an item to the end of the list.

insert()

List method that inserts an item at a specified index.

remove()

List method that deletes the first matching value.

pop()

List method that removes and returns the item at a given index.

del

Statement that deletes a variable or list element by index.

sort()

List method that arranges elements in ascending order in place.

sort(reverse=True)

List sort option that arranges elements in descending order.

List copy slicing

Using [:] to create a shallow copy of a list.

list.copy()

Built-in method returning a shallow copy of the list.

print()

Built-in function that outputs objects to the console.

len()

Built-in function returning the number of items in an object.

min()

Built-in function returning the smallest item of an iterable.

max()

Built-in function returning the largest item of an iterable.

range()

Function that returns an immutable sequence of numbers.

str()

Converts an object to its string representation.

int()

Converts an object to an integer.

float()

Converts an object to a floating-point number.

list()

Converts an iterable into a list.

• operator

Adds numbers or concatenates sequences.

• operator

Subtracts one number from another.

• operator

Multiplies numbers or repeats sequences.

/ operator

Divides numbers, returning a float result.

** operator

Exponentiation operator (power).

% operator

Modulus operator returning the remainder of division.

// operator

Floor division operator returning the quotient rounded down.

== operator

Comparison operator testing equality.

!= operator

Comparison operator testing inequality.

operator

Comparison operator testing greater than.

< operator

Comparison operator testing less than.

= operator

Comparison operator testing greater than or equal to.

Comparison operator testing less than or equal to.

string.upper()

Returns a copy of a string converted to uppercase.

string.lower()

Returns a copy of a string converted to lowercase.

string.title()

Capitalizes the first letter of each word in a string.

string.count()

Returns number of occurrences of a substring.

string.find()

Returns lowest index of a substring or -1 if not found.

string.replace()

Returns a copy of the string with occurrences replaced.

if statement

Executes a code block when its condition evaluates to True.

elif

Additional conditional branch following an if statement.

else

Branch executed when preceding conditions are False.

in operator

Checks membership of a value within a container.

for loop

Iterates over items in a sequence or iterable.

enumerate()

Returns pairs of index and item during iteration.

dict.items()

Dictionary method returning key–value pairs view.

while loop

Repeats a block as long as a condition stays True.

try-except

Error handling construct catching exceptions.

break

Loop control statement that exits the loop immediately.

continue

Loop control statement that skips to the next iteration.

pass

Null operation placeholder that performs no action.

def

Python keyword used to define a function.

return

Exits a function, optionally passing back a value.

import statement

Loads a module or object into the current namespace.

os.getcwd()

Returns the current working directory path.

os.listdir()

Lists files and directories for a given path.

os.makedirs()

Recursively creates directory/ies at the specified path.

dict.keys()

Returns a view object of dictionary keys.

dict.values()

Returns a view object of dictionary values.

dict.items() (dictionary)

Returns a view object of dictionary key–value tuples.

dict.update()

Adds or overwrites multiple key–value pairs.

dict.pop()

Removes and returns a value for the specified key.

dict.clear()

Removes all items from a dictionary.

dict.copy()

Returns a shallow copy of the dictionary.

and operator

Logical conjunction; True only if both operands are True.

or operator

Logical disjunction; True if at least one operand is True.

not operator

Logical negation that inverts a Boolean value.

Bitwise &

Binary AND on integers or element-wise logical AND on arrays.

Bitwise |

Binary OR on integers or element-wise logical OR on arrays.

Bitwise ~

Binary NOT that inverts bits or Booleans.

Pandas

Python library for high-level data manipulation and analysis.

Series

One-dimensional labeled array in pandas.

DataFrame

Two-dimensional labeled data table in pandas.

pd.read_csv()

Reads a CSV file into a pandas DataFrame.

df.head()

Returns the first n rows of a DataFrame.

df.tail()

Returns the last n rows of a DataFrame.

df.loc[]

Label-based selector for rows and columns.

df.T

Transposes rows and columns of the DataFrame.

df.drop()

Removes specified rows or columns from the DataFrame.

pd.concat()

Concatenates pandas objects along a particular axis.

df.merge()

Performs database-style join operations between DataFrames.

df.fillna()

Replaces missing (NaN) values with a specified value.

df.apply()

Applies a function along an axis of the DataFrame.

df.sum()

Computes sum of values over requested axis.

df.mean()

Computes mean of values over requested axis.

df.std()

Computes standard deviation over requested axis.

df.describe()

Generates descriptive statistics summary of DataFrame.

df.groupby()

Splits data into groups for aggregation or transformation.

df.plot(kind='box')

Creates a boxplot from DataFrame or Series data.

df.plot(kind='hist')

Creates a histogram from DataFrame or Series data.

df.plot(kind='pie')

Creates a pie chart from DataFrame or Series data.

plt.xticks()

Sets locations and labels of x-axis tick marks.