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Introduction to Python

Run the hidden code cell below to import the data used in this course.

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Take Notes

Add notes about the concepts you've learned and code cells with code you want to keep.

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# Add your code snippets here

Explore Datasets

Use the arrays imported in the first cell to explore the data and practice your skills!

  • Print out the weight of the first ten baseball players.
  • What is the median weight of all baseball players in the data?
  • Print out the names of all players with a height greater than 80 (heights are in inches).
  • Who is taller on average? Baseball players or soccer players? Keep in mind that baseball heights are stored in inches!
  • The values in soccer_shooting are decimals. Convert them to whole numbers (e.g., 0.98 becomes 98).
  • Do taller players get higher ratings? Calculate the correlation between soccer_ratings and soccer_heights to find out!
  • What is the average rating for attacking players ('A')?

Python Cheat Sheet

COMMENTS

Single line comments start with a '#'. Only the line with the '#' is considered as a comment.

This is a comment

''' Multiline comments are encased between triple quotes. Everything within the triple quotes is considered a comment. This is a multiline comment. '''

VARIABLES AND DATA TYPES

x = 5 # Integer: Whole numbers y = 5.0 # Float: Decimal numbers z = 'Hello' # String: Text b = True # Boolean: True or False values t = (1, 2, 3) # Tuple: Immutable sequence of values s = {1, 2, 3} # Set: Unordered collection of unique values

Type Conversion

a = str(x) # Converts x to string c = int(y) # Converts y to integer d = float(x) # Converts x to float

LISTS

List: Ordered collection of values

list1 = [1, 2, 3, 4, 5]

List Operations

len(list1) # Returns the length of list list1.append(6) # Appends 6 to end of list list1.insert(0, 0) # Inserts 0 at index 0 list1.remove(0) # Removes the first occurrence of 0 from the list list1.pop(0) # Removes and returns the element at index 0

TUPLES

Tuples are like lists, but they are immutable - their values can't be changed

tuple1 = (1, 2, 3)

SETS

Sets are unordered collections of unique elements

set1 = {1, 2, 3} set1.add(4) # Adds 4 to the set set1.remove(1) # Removes 1 from the set

STRINGS

s = 'Hello, World!'

String Operations

s[0] # Accesses first character of string s[1:5] # Slices string from index 1 to 4 (end index is exclusive)

DICTIONARIES

Dictionary: Collection of key-value pairs

dict1 = {'key1': 'value1', 'key2': 'value2'}

Dictionary Operations

dict1.get('key1') # Returns value for 'key1', or None if 'key1' is not present

CONDITIONALS

Used to perform different actions based on different conditions

if x < y: print("x is less than y") elif x > y: print("x is greater than y") else: print("x is equal to y")

LOOPS

For and While loops are used to iterate over a sequence (like a list, tuple, dictionary, set, or string) or perform a task multiple times

for i in list1: print(i) # Prints all elements in list1

for i in range(10): # Prints 0 through 9 print(i)

while x < 10: print(x) x += 1

List Comprehensions

List comprehensions provide a concise way to create lists based on existing lists

list2 = [i**2 for i in range(10)] # List of squares from 0 to 81

FUNCTIONS

Functions are blocks of code that only run when they are called

def add(a, b): return a + b

LAMBDA FUNCTIONS

Lambda functions are anonymous functions that are declared with the lambda keyword

add_lambda = lambda a, b: a + b # Equivalent to add function

CLASSES AND OBJECTS

Classes are user-defined data structures consisting of methods and attributes. Objects are instances of classes.

class MyClass: def init(self, a): self.a = a

def display(self):
    print(self.a)

obj = MyClass(5) obj.display() # Prints: 5

MODULES

Modules are Python .py files that consist of Python code. They can define functions, classes, and variables that you can reference in other Python .py files.

import math print(math.pi) # Prints: 3.141592653589793

EXCEPTION HANDLING

Exception handling is used to handle runtime errors that can occur in a program, to avoid program crashes and to provide meaningful error messages.

try: print(1/0) except ZeroDivisionError as e: print(e)

FILE I/O

Python provides functions to handle file I/O (Input/Output) operations

with open('filename.txt', 'r') as f: content = f.read() # Reads content from file

Python Mini Cheat Sheet: Array Indexing & Variable Definition

VARIABLE DEFINITION

# A variable must be defined before it can be used. Defining a variable means assigning it a value.
# Here's how to define a variable:

ages = [25, 30, 35]  # This is a list. Each element represents a person's age.

NUMPY ARRAYS

# Numpy is a library for the Python programming language, adding support for large, multi-dimensional arrays and matrices, 
# along with a large collection of high-level mathematical functions to operate on these arrays.
# Before you use numpy, you have to import it:

import numpy as np

# Convert the ages list to a numpy array
np_ages = np.array(ages)

# Now you can perform operations on this numpy array
discount_eligible = np_ages > 30  # Checks if each person is older than 30

ARRAY INDEXING

# In Python, you can access elements of a list or array using square brackets. 
# You put the index of the element you want inside the square brackets.

# For example, to print the first element of np_ages, you would do:
print(np_ages[0])

# You can also use arrays to index other arrays. 
# 'discount_eligible' is a boolean array that is True for each person older than 30, and False otherwise:

# Now, you can use the 'discount_eligible' array to index the 'np_ages' array. 
# This will give you only the elements of 'np_ages' where 'discount_eligible' is True:

print(np_ages[discount_eligible])  # This will print the ages of people who are older than 30