学习Python的第三天

学习Python的第三天，我开始深入Python的基本语法和特性，并通过编写一些简单的代码来加深理解。以下是我今天学习的一些代码案例：

1. 函数定义与调用

# 定义一个函数，计算两个数的和
def add_numbers(a, b):
    return a + b

# 调用函数
result = add_numbers(5, 3)
print("The sum is:", result)

2. 字符串操作

# 字符串拼接
str1 = "Hello, "
str2 = "World!"
combined_str = str1 + str2
print(combined_str)

# 字符串切片
text = "Python is a powerful language."
substring = text[7:13]  # 从索引7到索引12（不包含）
print(substring)

# 查找字符串中的子串
index = text.find("powerful")
if index != -1:
    print("Found 'powerful' at index:", index)
else:
    print("'Powerful' not found.")

# 字符串替换
new_text = text.replace("language", "programming language")
print(new_text)

3. 文件操作

# 写入文件
with open("example.txt", "w") as file:
    file.write("This is an example text.\n")
    file.write("Writing to a file in Python is easy.")

# 读取文件
with open("example.txt", "r") as file:
    content = file.read()
print(content)

# 逐行读取文件
with open("example.txt", "r") as file:
    for line in file:
        print(line, end='')  # end='' 用于避免额外的换行符

4. 条件语句与循环

# 条件语句
num = 10
if num > 5:
    print("The number is greater than 5.")
elif num == 5:
    print("The number is equal to 5.")
else:
    print("The number is less than 5.")

# 循环语句
for i in range(5):
    print(i)

# 使用while循环
count = 0
while count < 5:
    print(count)
    count += 1