Python小技巧整理（一）

目录

1.打印语句

2.for循环打印相同的变量

3.单独变量跟踪循环索引

4.for循环反转列表

5.for循环获取字符串的子字符串

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1.打印语句

        初级：打印多个变量，使用多个print() 语句。

a, b, c = 10, 5, 3

print(a)
print(b)
print(c)

# 10
# 5
# 3

        进阶：合理使用print()的参数。sep参数指定使用相同打印语句（上面的 a、b 和c）打印的各种变量之间的分隔符；end参数用于指定print语句的结束符。

a, b, c = 10, 5, 3
print(a, b, c, sep = "\n")

# 10
# 5
# 3 

print(a, end = "\n---\n")
print(b, end = "\n---\n")
print(c)

# 10
# ---
# 5
# ---
# 3

2.for循环打印相同的变量

        初级：

repeat = 10
a = "ABC"
for _ in range(repeat):
    print(a, end = "")

# ABCABCABCABCABCABCABCABCABCABC

        进阶：

repeat = 10
a = "ABC"

print(a*repeat)

# ABCABCABCABCABCABCABCABCABCABC

3.单独变量跟踪循环索引

        初级：创建range迭代器来跟踪索引

list = ["a", "b", "c", "d", "e", "f"]

for index in range(len(list)):
    print("index =", index, "value =", list[index], sep = " ")
    index += 1

# index = 0 value = a
# index = 1 value = b
# index = 2 value = c
# index = 3 value = d
# index = 4 value = e
# index = 5 value = f

        进阶：使用enumerate()方法跟踪索引index和值i 

list = ["a", "b", "c", "d", "e", "f"]

for index, i in enumerate(list):
    print("index =", index, "value =", i, sep = " ")

# index = 0 value = a
# index = 1 value = b
# index = 2 value = c
# index = 3 value = d
# index = 4 value = e
# index = 5 value = f

4.for循环反转列表

        初级：反向迭代列表并将元素添加到新列表

input_list  = [1, 2, 3, 4, 5]
output_list = []

for idx in range(len(input_list), 0, -1):
    output_list.append(input_list[idx-1])

print(output_list)

# [5, 4, 3, 2, 1]

        进阶：Python 中的切片实现（reverse()方法也可以实现）

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

output_list = input_list[::-1]
print(output_list)

# [5, 4, 3, 2, 1]

input_list.reverse()
print(input_list)

# [5, 4, 3, 2, 1]

5.for循环获取字符串的子字符串

        初级：

input_str = "ABCDEFGHIJKL"
start_index = 4
n_chars = 5

output_str = ""

for i in range(n_chars):
    output_str += input_str[i+start_index]

print(output_str)

# EFGHI

        进阶：

input_str = "ABCDEFGHIJKL"
start_index = 4
n_chars = 5

output_str = input_str[start_index:start_index+n_chars]
print(output_str)

# EFGHI