Commonly Used Python Functions and Examples for Beginners

Beginners often get stuck when writing code because they cannot recall which built‑in function to use for a given task; this guide compiles more than 100 common Python functions into twelve sections, providing short examples that can be reviewed daily to reinforce memory.

1. Basic Functions

Example: convert a floating‑point number to a string and print its type.

<code>f = 30.5
ff = str(f)
print(type(ff))  # output: class 'str'</code>

2. Control Flow

Example: grade a score entered by the user with multiple conditional branches.

<code>s = int(input("请输入分数:"))
if 80 >= s >= 60:
    print("及格")
elif 80 < s <= 90:
    print("优秀")
elif 90 < s <= 100:
    print("非常优秀")
else:
    print("不及格")
    if s > 50:
        print("你的分数在60分左右")
    else:
        print("你的分数低于50分")</code>

3. Lists

Example: find the index of the number 6 within a list.

<code>l = [1,2,2,3,6,4,5,6,8,9,78,564,456]
n = l.index(6, 0, 9)
print(n)  # output: 4</code>

4. Tuples

Example: slice a tuple, convert it to a list, modify the list, and convert back to a tuple.

<code># take elements with indices 1‑3 and convert to list
t = (1,2,3,4,5)
print(t[1:4])
l = list(t)
print(l)
# replace element at index 2 with 6
l[2] = 6
print(l)
# convert back to tuple
t = tuple(l)
print(t)</code>

5. Strings

Three ways to use format() for string interpolation.

<code>"{0} 嘿嘿".format("Python")
a = 100
s = "{0}{1}{2} 嘿嘿"
s2 = s.format(a, "JAVA", "C++")
print(s2)  # 100JAVAC++ 嘿嘿

s = "{}{}{} 嘿嘿"
s2 = s.format(a, "JAVA", "C++", "C# ")
print(s2)  # 100JAVAC++ 嘿嘿

s = "{a}{b}{c} 嘿嘿"
s2 = s.format(b="JAVA", a="C++", c="C# ")
print(s2)  # C++JAVAC#  嘿嘿</code>

6. Dictionaries

Example: retrieve a value with dict.get() providing a default.

<code>d = {"name": "小黑"}
print(d.get("name2", "没有查到"))  # 没有查到
print(d.get("name"))            # 小黑</code>

7. Functions

Illustrates a custom function that defines a global variable.

<code>def fun1():
    global b
    b = 100
    print(b)
fun1()
print(b)  # both prints 100</code>

8. Processes and Threads

Example of creating a thread by subclassing threading.Thread .

<code>class MyThread(threading.Thread):
    def __init__(self, name):
        super().__init__()
        self.name = name
    def run(self):
        for i in range(5):
            print(self.name)
            time.sleep(0.2)

t1 = MyThread("凉凉")
t2 = MyThread("最亲的人")
t1.start()
t2.start()</code>

9. Modules and Packages

Example of importing a module from a package and using its attributes.

<code>from my_package1 import my_module3
print(my_module3.a)
my_module3.fun4()</code>

10. File Operations

Brief overview of common file modes, file object attributes, and methods, followed by a mention of the os module for directory handling.

11. Decorators / Class Methods

Demonstrates the use of @classmethod to access class variables.

<code>class B:
    age = 10
    def __init__(self, name):
        self.name = name
    @classmethod
    def eat(cls):
        print(cls.age)

b = B("小贱人")
b.eat()  # prints 10</code>

12. Regular Expressions

Using re.split() to split a string.

<code>import re
s = "abcabcacc"
l = re.split("b", s)
print(l)  # ['a', 'ca', 'cacc']</code>

The purpose of this article is to help readers quickly memorize the names and purposes of frequently used Python functions; detailed usage can be looked up as needed, allowing a more purpose‑driven learning approach.