Quickly master the key knowledge points of Pandas data filtering

Quickly master the key knowledge points of Pandas data filtering, requiring specific code examples

Overview:
Pandas is a powerful data analysis library that provides a wealth of features and tools to process and analyze data. Among them, data filtering is one of the important operations in Pandas, which can help us extract the information we are interested in from the data. This article will introduce the key knowledge points of data filtering in Pandas and provide specific code examples to help readers quickly master this important skill.

1. Use Boolean index to filter data
   Boolean index is a filtering method based on conditional expressions, which can filter data according to a certain condition. The following is a sample code that uses a Boolean index to filter data:

import pandas as pd

# 创建一个示例数据
data = {'name': ['Alice', 'Bob', 'Charlie', 'David'],
        'age': [25, 30, 35, 40],
        'gender': ['F', 'M', 'M', 'M']}
df = pd.DataFrame(data)

# 筛选age大于30的数据
age_filter = df['age'] > 30
filtered_data = df[age_filter]
print(filtered_data)

Output results:

      name  age gender
2  Charlie   35      M
3    David   40      M

2. Use the isin() method to filter data
   isin() method can Used to check whether the value in a certain column is in the given list, a Series of Boolean values ​​will be returned, indicating whether each value meets the conditions. The following is a sample code that uses the isin() method to filter data:

import pandas as pd

# 创建一个示例数据
data = {'name': ['Alice', 'Bob', 'Charlie', 'David'],
        'age': [25, 30, 35, 40],
        'gender': ['F', 'M', 'M', 'M']}
df = pd.DataFrame(data)

# 筛选name在给定列表中的数据
filter_names = ['Alice', 'Charlie']
filtered_data = df[df['name'].isin(filter_names)]
print(filtered_data)

Output results:

      name  age gender
0    Alice   25      F
2  Charlie   35      M

3. Use conditional expressions to filter data
   In addition to the above two Commonly used methods, Pandas also provides a more flexible way to filter data with conditional expressions. You can use comparison operators (such as >,

import pandas as pd

# 创建一个示例数据
data = {'name': ['Alice', 'Bob', 'Charlie', 'David'],
        'age': [25, 30, 35, 40],
        'gender': ['F', 'M', 'M', 'M']}
df = pd.DataFrame(data)

# 筛选年龄大于30且性别为男性的数据
filtered_data = df[(df['age'] > 30) & (df['gender'] == 'M')]
print(filtered_data)

Output results:

      name  age gender
2  Charlie   35      M
3    David   40      M

4. Use the query() method to filter data
   query() method You can use SQL-like syntax to filter data, which can filter data more intuitively and concisely. The following is a sample code that uses the query() method to filter data:

import pandas as pd

# 创建一个示例数据
data = {'name': ['Alice', 'Bob', 'Charlie', 'David'],
        'age': [25, 30, 35, 40],
        'gender': ['F', 'M', 'M', 'M']}
df = pd.DataFrame(data)

# 使用query()方法筛选年龄大于30且性别为男性的数据
filtered_data = df.query('age > 30 and gender == "M"')
print(filtered_data)

Output results:

      name  age gender
2  Charlie   35      M
3    David   40      M

Summary:
This article introduces the key knowledge points of data filtering in Pandas , and provides specific code examples. By mastering these knowledge points, readers can extract the required information from large amounts of data more efficiently. I hope this article can help readers quickly master the skills of Pandas data screening and improve their data analysis capabilities.

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