Week 2 Python Fundamental

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Week 2: Python Fundamental Part 1

1. Variables¶

Variable in Python store data values

print() is a built-in function in python

In [35]:

x = 'summer'
print(x)

x = 'summer' print(x)

summer

2. Numeirc¶

2.1 Integer¶

we can use the built-in type() function to identify the type of variable

In [1]:

a = 3
type(3)

a = 3 type(3)

Out[1]:

int

2.2. float¶

In [42]:

c = 6.3
type(c)

c = 6.3 type(c)

Out[42]:

float

2.3 Python Arithmetic Operators¶

The common mathematical operations can be completed by aritemetic operatos in Python

Python Arithmetic Operators

In [25]:

3 + 5

3 + 5

Out[25]:

8

In [26]:

8/4

8/4

Out[26]:

2.0

3. Strings¶

Strings in python are surrounded by either double quotation marks, or single quotation marks

In [32]:

print("Hello")
print('Hello')

print("Hello") print('Hello')

Hello
Hello

In [28]:

strs_ex = "It's an apple"

print(type(strs_ex))
print(len(strs_ex))

strs_ex = "It's an apple" print(type(strs_ex)) print(len(strs_ex))

<class 'str'>
13

A number with quotation or without quotation is different

In [7]:

num = 3
str_3 = '3'
print(type(num))
print(type(str_3))

num = 3 str_3 = '3' print(type(num)) print(type(str_3))

<class 'int'>
<class 'str'>

3.1 Slicing strings¶

In [60]:

# Slicing: Return a range of characters by using the slice syntax
x = "Clark is pretty good"
print(len(x))
print(x[1:3])

# Slicing: Return a range of characters by using the slice syntax x = "Clark is pretty good" print(len(x)) print(x[1:3])

20
la

In [8]:

# Slice from the start
b = "Hello, Python!"
print(b[:5])

# Slice to the end
print(b[2:])

# Negative indexing
print(b[-5:-2])

# Slice from the start b = "Hello, Python!" print(b[:5]) # Slice to the end print(b[2:]) # Negative indexing print(b[-5:-2])

Hello
llo, Python!
tho

Exercise 1: Get the characters from string

1. Get the character that index is 0 in x = "Clark is pretty good"

3.2 String Concatenation¶

In [53]:

a = "Level"
b = "Up"
c = a + b
print(c)
d = a + ' ' + b
print(d)

a = "Level" b = "Up" c = a + b print(c) d = a + ' ' + b print(d)

LevelUp
Level Up

3.3 Combine of string and number¶

In [9]:

age = 36
txt = "My name is John, I am " + age
print(txt)

age = 36 txt = "My name is John, I am " + age print(txt)

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[9], line 2
      1 age = 36
----> 2 txt = "My name is John, I am " + age
      3 print(txt)

TypeError: can only concatenate str (not "int") to str

Exercise 2: Type conversion

1. We have used built-in function like print() and type() to do task, this time we use str() to convert a value to string
2. Use str() function to remove the error

In [1]:

# F-Strings
age = 5
txt = f"I have lived here for {age} years"
print(txt)

# F-Strings age = 5 txt = f"I have lived here for {age} years" print(txt)

I have lived here for 5 years

3.4 Methods for String¶

A method is a special type of function, it allow you to do different things with different objects.

We can use methods through dot notation: variable.method()

In [ ]:

names = "Clark"
u_names = names.upper()
print(u_names)

names = "Clark" u_names = names.upper() print(u_names)

Methods for String in Python Documentation

Exercise 3: Try methods for String

1. get lowercase of string names = "Clark' use lower()

💡 Tip: Guidelines for Variables¶

• Python is case-sensitive (apple and Apple are two separate variables).
• Use meaningful variable names (e.g. university is clearer than a_string). Ideally, you code and variable names should be meaningful.
• Avoid using variable names that conflict with existing python functions or keywords (e.g., print, type).

4. Boolean¶

• The expression in Python is True and False

In [61]:

print(5 > 3)

print(5 > 3)

True

• Most Values are True

In [64]:

print(bool("abc"))
print(bool(123))
print(bool(["apple", "cherry", "banana"]))

print(bool("abc")) print(bool(123)) print(bool(["apple", "cherry", "banana"]))

True
True
True

• Empty values are False

In [65]:

print(bool(False))
print(bool(None))
print(bool(0))
print(bool(""))
print(bool(()))

print(bool(False)) print(bool(None)) print(bool(0)) print(bool("")) print(bool(()))

False
False
False
False
False

5. List¶

In [13]:

myclass = ['python', 'statistics', 'mapping', 'mapping']
print(myclass)
print(len(myclass))

myclass = ['python', 'statistics', 'mapping', 'mapping'] print(myclass) print(len(myclass))

['python', 'statistics', 'mapping', 'mapping']
4

In [ ]:

mynote = ["python", 10, True, 'mapping', 23]

mynote = ["python", 10, True, 'mapping', 23]

5.1 Change list items¶

In [66]:

grocery_shops = ["Whole Foods", "Trader Joe's", "Stop & stop", "Kroger"]
grocery_shops[1] = "Wegmans"

grocery_shops = ["Whole Foods", "Trader Joe's", "Stop & stop", "Kroger"] grocery_shops[1] = "Wegmans"

In [36]:

#### 5.2 Sort the list
fruits = ['apple', 'orange', 'blueberries', 'Mangoes']
fruits.sort(reverse=True)
print(fruits)

#### 5.2 Sort the list fruits = ['apple', 'orange', 'blueberries', 'Mangoes'] fruits.sort(reverse=True) print(fruits)

['orange', 'blueberries', 'apple', 'Mangoes']

In [33]:

fruits.sort(reverse=True)
print(fruits)

fruits.sort(reverse=True) print(fruits)

['orange', 'blueberries', 'apple', 'Mangoes']

Exercise 4: Try method for list

1. Append kroger to list grocery_shops = ["Whole Foods", "Trader Joe's"] use append()

6 Dictionaries¶

• Dictionaries store data value in key:value pairs
• Access value using the key
• Dictionaries cannot have two items with the same key:

In [15]:

university = {
  "name": "clark",
  "location": 'MA',
  "location": "worcester",
  "year": 1887,
  'major': ['GIS', 'sociology', 'computer science']
}
 
print(university['name'])
print(university['major'])
print(university)

university = { "name": "clark", "location": 'MA', "location": "worcester", "year": 1887, 'major': ['GIS', 'sociology', 'computer science'] } print(university['name']) print(university['major']) print(university)

clark
{'name': 'clark', 'location': 'worcester', 'year': 1887}

6.1 Adding items¶

In [17]:

university['room'] = 'BP310'
print(university)

university['room'] = 'BP310' print(university)

{'name': 'clark', 'location': 'worcester', 'year': 1887, 'room': 'BP310'}

6.2 Methods for dictionaries¶

In [ ]:

university = {
  "name": "clark",
  "location": "worcester",
  "year": 1887
}

university = { "name": "clark", "location": "worcester", "year": 1887 }

In [23]:

### Get keys
key_un = university.keys()
key_un

### Get keys key_un = university.keys() key_un

Out[23]:

dict_keys(['name', 'location', 'year', 'room'])

In [42]:

### Dictionaries in Dictionaries
university = {
  "name": "clark",
  "location": "worcester",
  "year": 1887, 
  "description": {'student':3827, 'intro':'''Founded in 1887, Clark offers undergraduate and graduate
                  programs with a focus on interdisciplinary studies,
                  research opportunities, and community engagement'''}}

### Dictionaries in Dictionaries university = { "name": "clark", "location": "worcester", "year": 1887, "description": {'student':3827, 'intro':'''Founded in 1887, Clark offers undergraduate and graduate programs with a focus on interdisciplinary studies, research opportunities, and community engagement'''}}

In [43]:

print(university['description']['intro'])

print(university['description']['intro'])

Founded in 1887, Clark offers undergraduate and graduate
                  programs with a focus on interdisciplinary studies,
                  research opportunities, and community engagement

Exercise 5: Try methods for Dictionaries

1. Use values(), items() to get value and item from university