Python Basic Data Types: Strings, Numbers, Lists, Tuples, and Dictionaries with Examples

String Type

A string is a sequence composed of one or more elements.

Strings are typically delimited by single quotes, double quotes, triple single quotes, or triple double quotes.

Escape Characters

r disables escape sequences

\n newline

\b backspace

\r carriage return

\t tab

\? a question mark

Practice Code

str1 = "Hello World !"
str2 = '''   ssss
sssssss'''
print(str1,str2)
str3 = "你好 中国"
print(str3)

# slicing
str4 = "hello I am zhangsan!"
print(str4[8])
print(str4[:5])  # end index is exclusive, start index 0 can be omitted.
print(str4[5:])    # start index includes the element at position 5.
print(str4[-10:-1])

# concatenation
str5 = "Hello"
str6 = "World !"
str7 = "123"
print(str5 + ' ' +  str6 + str7) # string concatenation cannot mix with int types

# string formatting
name = "zzzz"
age = 123

newage = str(age)     # str() converts to string
print(type(newage))

print("my name is %s, my age is %d" %(name,age))  # %s for string, %d for number

msg = "my name is {0}, my age is {1}".format(name,age)
print(msg)

# escape characters
new1 = r"abc 
 cba"
print(new1)

Built-in Functions

capitalize()

count()

decode()

encode()

endswith()

startswith()

find()

index()

isalpha()

lstrip()/rstrip()/strip()

replace()

upper()

split()

reponse = "  abcd123  45abcd  "
print(reponse.capitalize())   # capitalize first character
print(reponse.count('b',2,len(reponse)))    # count occurrences of 'b' between positions
print(reponse.encode(encoding="UTF-8"))   # encode string with UTF-8
newreponse = reponse.encode(encoding="UTF-8")
print(newreponse.decode(encoding="UTF-8"))   # decode back to string
print(reponse.startswith("b"))  # check prefix
print(reponse.endswith("c"))    # check suffix
print(reponse.find("ac"))   # find substring, returns -1 if not found
print(reponse.index('b'))  # return index of first occurrence
print(reponse.isalpha())   # check if all characters are alphabetic
print(reponse.lstrip())  # remove leading spaces
print(reponse.rstrip())  # remove trailing spaces
print(reponse.strip())   # remove both leading and trailing spaces
print(reponse.replace("  ",""))  # replace double spaces
print(reponse.upper())  # convert to uppercase
print(reponse.split("  "))   # split by double spaces into list

Numeric Types

Categories

Integer

Boolean

Float

Complex

Operators

+ - * / %

> = < >= <= ==

Practice Code

age = 45    # positive integer
memory = -100   # negative integer
a = 0x768A   # hexadecimal integer
print("my age is : %d, my memory is : %d" % (age,memory))
print(a)

a = True
b = False
print(int(a),int(b))

c = 1.2
d = 2.4
print(c,type(d))


a = 123
b = 456

print("a + b = " + str(a+b) )
print("a - b = " + str(a-b))
print("a * b = " + str(a*b))
print("a / b = " + str(a /b) )

print("a > b " + str(a > b))
print("a < b " + str(a<b))

List Type

Built-in Functions

append()

count()

extend()

index()

insert()

pop()

remove()

reverse()

Practice Code

## definition
a = []
print(type(a))

numlist = [1,2,3,4,5,6]
strlist = ["a","b","c","d"]

print(numlist,strlist)

## access elements
print(numlist[3],strlist[2])
print(numlist[:5])
print(len(numlist))

## application
ipAddress = [r"192.158.0.1",r"192.168.0.2"]
print(ipAddress)

## iteration
for ip in ipAddress:
    print(ip)

# built-in functions

testHosts = ["aa","bb","cc","dd"]
t1 = ["dd","cc"]

testHosts.append("EE")   # append at end
print(testHosts.count('bb'))   # count occurrences
print(testHosts.extend(t1))    # extend list
print(testHosts.index("EE"))   # get index of element
testHosts.insert(5,"DD")  # insert at position 5
print(testHosts)
print(testHosts.pop(2))   # pop element at index 2
print(testHosts)
testHosts.remove("EE")  ## remove element
print(testHosts)
testHosts.reverse()  # reverse list
print(testHosts)

Tuple Type

Elements in a tuple are immutable.

# definition
a = ()
print(type(a))

a = (1,2,3,4,5)
b = ("aa","bb","cc")

print(a,b)

# usage
test = ("java","tomcat","springboot")
print(test[1])
print(test[:2])

test1 = ([1,2,3],"aa")
print(test1)
test1[0].append(123)
print(test1)

Dictionary Type

key/value pairs

Built-in Functions

clear()

copy()

get()

items()

keys()

update()

pop()

values()

Practice Code

# definition

a = {}
print(type(a))

myinfo = {"name":"zhangsan","age":45}
print(myinfo)
print(myinfo['name'])

myinfo["job"] = "devops1"    # add or modify element
print(myinfo)

# built-in functions
myinfo = {"name":"zhangsan","age":45}

#print(myinfo.clear())   # clear dictionary
print(myinfo)

data1 = myinfo.copy()   # copy independent version
print(data1)

data1["name"] = "lisi"
print(data1)
print(myinfo)

print(myinfo.get("name"))  # get value by key

print(myinfo.items())  # return view of (key, value) tuples
print(type(myinfo.items()))

print(myinfo.keys())   # get all keys
print(myinfo.values())  # get all values

print(myinfo.pop("name"))  # remove entry by key
print(myinfo)

Practical 1 – Python Formatted Output

## %
name = "zhangsan"
age = 45

print("my name is : %s , my age is %s" % (name,str(age)))

## format

name = "lisi"
age = 34
print("my name is {0}, my age is {1}".format(name,age))


## title
info = """
name = {0}
age = {1}
high = {2}
jobs = {3}
address = {4}
"""
print("---------------------")
print(info.format("zhangsan",24,178,"PythonDeveloper","Beijing"))
print("---------------------")

Practical 2 – List CRUD Operations

## append
## remove  pop

students = ["zhangsan","lisi","wangwu"]

## add a student
newStudent = "aa"
students.append(newStudent)
print("class students is : %s " %(students,))

## merge classes
twoStudents = ["cc","dd","ee"]
students.extend(twoStudents)
print("class students is : %s " %(students,))

## remove a student
moveStudent = "wangwu"
students.remove(moveStudent)
print("class students is : %s " %(students,))

## update
studentName = "zhangsanfeng"
stuindex = students.index("zhangsan")
students[stuindex] = studentName
print("class students is : %s " %(students,))

Practical 3 – Converting JSON Data to a Dictionary

import json

## dict -> json
myinfo = {"name":"zhangsan","age":100}
jsonInfo = json.dumps(myinfo)
print(type(jsonInfo))

## json -> dict
dictInfo = json.loads(jsonInfo)
print(type(dictInfo))
print(dictInfo['age'])

##
a = '{"name":"zhangsan"}'
print(json.loads(a))