How to Remove Blank Lines from Text

Sources of Blank Line Problems

Blank lines appear in text for many reasons: copying from PDF or Word documents preserving format line breaks; repeated pasting of text adding duplicate separator lines; line ending differences between old software or different systems; program-generated text with extra blank line separators; database exports automatically inserting blank lines between records.

Two Processing Needs

There are two different goals for blank line processing: delete all blank lines (suitable for compact no-spacing formats needed in some data processing pipelines); or compress consecutive multiple blank lines to a single blank line (preserving single-line paragraph separators while only deleting redundant duplicate blank lines — the more common need). Online tools typically provide both options.

What Is a "True" Blank Line

A line that looks blank is not necessarily truly empty. A line may contain invisible characters: one or more spaces, tab characters, or non-breaking spaces. These "pseudo-blank lines" are invisible to the eye but cause simple "remove blank lines" operations to miss them. The correct approach: if a line's content after trimming (removing leading and trailing whitespace) is an empty string, treat it as a blank line and delete it.

Command-Line Tools

# 删除所有空行（包括只含空格的行）
grep -v '^\s*$' input.txt > output.txt

# 使用 sed 删除空行
sed '/^\s*$/d' input.txt > output.txt

# 将连续多个空行压缩为一个空行
cat -s input.txt  # macOS/Linux（-s: 连续空行压缩为一行）

# 或使用 sed
sed '/^$/N;/^\n$/d' input.txt > output.txt

Python Code Implementation

# 删除所有空行
def remove_all_blank_lines(text):
    lines = text.splitlines()
    return '\n'.join(line for line in lines if line.strip())

# 压缩连续空行为单个空行
def compress_blank_lines(text):
    import re
    return re.sub(r'\n{3,}', '\n\n', text)  # 3个以上换行符变为2个

# 综合处理：先压缩，再去除首尾多余空行
def clean_blank_lines(text):
    import re
    text = re.sub(r'\n{3,}', '\n\n', text)  # 压缩多余空行
    return text.strip()  # 去除首尾空白

Processing in Word and Document Editors

In Microsoft Word, use the Find and Replace function to batch delete blank lines: open Find and Replace (Ctrl+H), enter ^p^p (two paragraph marks, representing a blank line) in the Find field, enter ^p (one paragraph mark) in the Replace field, and click "Replace All" multiple times until no more replacements occur. This compresses consecutive blank lines to a single blank line.

Blank Line Management in Code Files

In code files, blank lines are meaningful formatting elements used to separate functions, classes, and logical blocks. Python PEP 8 specifies: two blank lines between top-level function and class definitions; one blank line between methods within a class; logical groupings within functions may be separated by one blank line. Code auto-formatters (like black, prettier) automatically normalize blank line counts to maintain consistent code style.